After having manually backup my site, my site can't accept any resister and net work admin&

Hey
I hope you having a good day.
I am currently facing an strange issue.
After having a backup manually with SnapShot Pro, my site can't register any one, and only network admin can't login to my site.

Other super admins and users still can log in to my site.
This is happening after starting using membership Pro2 and CoursePress Pro.

However, I can't figure out the reason why!

So I need your help.
When, I make a restoring with SnapShot back up file, this issues is not fixed, but I could fix this with server side backup option.

I have experienced 3 times about the problem. And all 3 times happened after using Snapshot Pro manually.

I want to try to figure out the reason with support.

King Regards

KAZUKI

* I could fix this with my last backup file, which is also manual backup option.

I don't know still who this is happening, but my configuration about backup option might be wrong.
Is there something to care about backup option?
Or, is this cacheing?

Any way, I have no idea.

* It must be database issue, my file was no problem.