seedling

You could give it a root booster.The best on the market is House and Garden Roots Excellarator.I soak my cubes in it before a introduce the popped seed.Root booster really help to improve seedling health and strength.Iv not grown without them for almost 20yrs.

Too early to give anything but water. Wait and see if she starts moving or pull it and plant another that's the reality.

agree with Organoman

No picture, no diary.........impossible to answer properly. However, some seeds just don't make it! Always, always plant more seeds than you think you will need for this very reason.

I would say just be patient also over watering can cause seedling to stunt and grow super slow. I like to get soil damp b4 putting seeds in the soil I get seeds started in a pepper towel when root is 1cm then I put in a solo cup of pre wetted soil I put the seed barely under some soil and just put a shot glass of water on top that enough to make the soil on top the seedling to kinda encase it If you do it like this you will not need to water the soil for the 1st week or so. I would recommend that you let the soil get pretty dry b4 watering next time by then hopefully the plant will have another or 2 more sets of leaves Good luck Just remember be patient and have fun it will take a long time to master growing so don’t get stressed the whole time that will kill the fun

I guess its just a matter of time. In 30yrs Iv never had a seedling refuse to grow, Iv had pythium but you'd notice that straight away as the first sign is a mushy stem that fails to hold itself up. Get the temps up,24 is best, under 20 will stall it.Don't keep the soil soaked, let it dry out to some degree. Not a lot to go on though.

A picture maybe?..

some seedlings just stall out. make sure to keep the humidity raised, maybe even cover with a clear bottle or ziplock bag to act as a humidity dome

A diary or at least a photo could help us help you