Identical problem here. Went through the instructions to reinstall but no change. I have a brand new Tab A and can launch Minecraft from my admin account but not my son's restricted account. I have a different Tab A setup for my daughter and have no problem launching it from her restricted account.
I resolved this by re-creating the restricted profile. I was also having a problem where the profile was not able to see my Google account when using Youtube Kids, but this is also now fixed.