Warmth matters more than most beginners realise, and indica seeds left on a cold windowsill in March will often rot before they open. Somewhere between 22 and 26 degrees is the range that gets me consistent results, usually from a cheap heat mat with a towel on top. Temperature logs from a handful of germination trials are summarised on https://kushindicaseeds.com, and success dropped sharply below 20 degrees. Too hot is also a problem, so a thermometer next to the tray is worth the few dollars.