Is there a chain keeper or chain guide available for a single sprocket E bike type frame bike to stop chain from coming of the front single sprocket?
If your chain is coming off of the single front sprocket, you probably need to tighten the chain or get a new chain.
Use a chain checker to see if your chain is stretched out and needs to be replaced. If not, some bike frames have a longer space instead of just a single hole where the back wheel can move a bit. Just loosen the back wheel and see if it can move back a bit and tighten it in place. But I'd doubt an e-bike would have that kind of variability.
If none of that works, you may need to ask the bike shop to look it over. There may be many other reasons this is happening.