MIUI 10 9.2.21. This also happened on 9.2.15 which sometimes, play store won't download even though data is enabled. I can't use reverse tethering since it always says waiting for network.
What do you mean by "reverse tethering"?
I assume you are having this problem while on Mobile data?
My wife had this problem for a while last fall on her Mi Note 3 running EU stable, with an unlimited data plan.
Temporary solution was to connect the phone to a wifi somewhere when she wanted to update stuff on Playstore.
We eventually fixed it, but I don't remember what we did.
Or maybe it fixed itself after some update.
Do you have a data plan set, monthly or with daily limits?
If so, check that there are no hard limits set too low somewhere.
Set Play store, etc., to "ignore" in:
Settings/Sim cards/set data plan/ data plan/custom data plan/Ignore data usage
This "should" only affect what usage is reported, but maybe it affects more.
In some weekly update last fall, many (after a dirty flash) got the problem of not being able to change their data plan.
Solution was to clear all data for the Securities app.
The settings for the data plan seems to be kept in it.
You might want to try that.