Had multiple duds due to igniters burning but not igniting the motors. They were. Carefully seated. Estes igniters and motors. Are there other brands? What’s your favorite?
Estes igniters are the absolute worst. Fortunately, BP is pretty easy to get jump started and burning.
I wash the white cornstarch/glue "pyrogen" off newer Estes igniters & dip them in an NC lacquer/BP/MgAl powder slurry for Estes and homemade BP motors. Al powder gets pretty hot too and will work, but the MgAl alloy burns hotter and throws a bunch of sparks, without the reactivity and potential long-term storage issues of pure Mg. You can "perc up" your slurry if you want a little extra oxygen in the mix. BP granules are 3Fg or 4Fg commercial or -40 mesh to dust if you make your own. Fires up easily off of a 6-volt unit, better off of a 9V, but I usually use a 12V lead-acid scooter battery for instant ignition, though LiPos have lower internal resistance. And a roll of nichrome 80 (I use 34-40 gauge) is about $10 for a 500-foot roll, which will last you quite awhile. Smaller gauge has higher resistance and heats up faster but is more difficult to work with if you have fat fingers. And nichrome doesn't solder easily, though it's possible with an acid flux and silver solder, but I'm good with just wrapping and crimping. Kanthal is an FeCrAl alloy that has a lower resistance than nichrome but withstands high temperatures better (I'll sometimes reuse igniter wires if they're not burned through, but gotta wash the corrosive BP burn products off of them), and might be easier to solder if that's your thing. It's easy to find online, or at smoke shops--it's often used for wire heating coils in vape pens/pipes. So long as you know your wire length/gauge/resistance and your battery characteristics, you can calculate the minimum power delivery needed. I generally overshoot with current delivery with a healthy margin, because I don't like waiting seconds after I push the button for a rocket to launch. But they'll launch off 6 volts of alkaline batteries if that's all you have handy.
With Estes motors, simply pouring a little bit of 4Fg or meal powder down the throat and stuffing a stock igniter or a piece of cannon fuse in it typically works, too. If fusing, some motor classes have a very narrow throat so you'd need the thinner small-diameter visco fuse that's available online (cannonfuse.com's as good as any for small amounts). Primative but functional, and how it used to be done. Make sure your launch stand is solid so no surprise launch rod tilting! Wouldn't try that for APCP composite motors--you need a hotter mix than plain BP and you absolutely want top-down ignition (igniter rammed deep inside), so gravity is not your friend in this case. If fusing BP motors, don't skimp on fuse length too much. Those baby motors will still scorch the skin off your hands with the quickness. You don't want your hands under there. Use a camping lighter or propane torch for extra distance. Don't try this at an NAR or Tripoli sponsored launch--you'll get scolded by a hundred grannies and men acting like grannies for overtly breaking one of the NAR 10 Commandments on safe rocketry practices. This is by forum definition a "research" project.
These NC/BP/MgAl igniters typically work very well for Quest/Aerotech APCP composite motors, too, but you need to fashion them so you can slide them all the way up the core of the motor for good top-down ignition. No matter what you're igniting, test out several from any batch far away from any motor so you know precisely how they behave. Good idea to assess igniter and total ignition system resistance; easy with a simple multimeter. Please do not attempt a clustering ignition unless you have 100% knowledge and confidence in your ignition system, including igniter characteristics. Seems from your description that they're heating up. Do they glow brightly when powered up outside a motor?
If you're mostly into finned rockets and not fireworking, you probably don't have any MgAl laying around. NC is easily made by dissolving single-base (NC only) or double-base (more common, NC + NG) in acetone to 5% by weight (or eyeball it). Some use ping-pong balls (celluloid, which is low-nitration NC) but most on the market are no longer NC--they need to smell like camphor (stabilizer) and burn cleanly themselves without residue. The plastic ones will not work. Dollar store fingernail polish remover works fine, though read the label to make sure it is only acetone and doesn't have a bunch of other crap in it (or added water). Acetone is hygroscopic and happily absorbs atmospheric moisture, so keep the lid closed when not in use. You can also buy it at HD or Lowes. For smokeless/NC powders, you want the thin flakey stuff made for shotshells--the hard extruded pellets made for magnum rifles will take forever to dissolve, but eventually will. If you don't make your own, BP can be purchased at a sporting goods store, though it's harder to locate than smokeless powder due to shipping/storage restrictions. Common brands are Goex and Old Ensford. Bad homemade BP
might work, but I wouldn't trust it. Most people who self-teach themselves how to make BP make pretty crummy stuff. My BP's pretty hot, so that's never a concern. MgAl and Al can be purchased from any fireworking chem vendor online, but you don't need all that much and a pound minimum order would last quite a long time (unless you're building other fireworks or experimenting with novel propellants!). I'm happy to send you a small quantity of MgAl to test out if you PM me details. BP I will not mail.
There's also several videos online about making igniters that are variable in quality and safety practices. Some are ok. Ask if you're unsure.
And like the folks below inquired--what's your electrical system? Estes igniters
usually do the trick, especially if you ram a few extra amps down the wires, but that's not sufficient for me. And no way would I ever spend a buck or more for an extra igniter (to accommodate Estes' crummy igniter quality) when they cost about 2 cents to make. C'mon--a piece of wire with a dab of cornstarch glued on? Ridiculous. And what do your igniters look like after a launch attempt? Are they heating but just not firing the propellant grain or are you not getting juice to the igniter at all? You checked your battery output, right?