Grass won't spread - Sync world/Realm

This is for most recent version of better together:

Grass won't spread. At first it was working just fine.

-Place a few blocks of dirt on grass
-It will not spread at any light level

First, my friend had a Realm with a newly generated world. We played there for about 7 days, then none of the grass would spread and my dirt remained empty. So I don't know why this glitch happened after a few does and not immediately.

Now, my own world, that was first synced, then added to a Realm, has the same problem. Grass will not spread from grass to dirt blocks, under any circumstances.

Thank you.