"Could Not Sign In" to App Store

If your issue has been addressed, I would greatly appreciate it if you could relay the process to me as well.

I am contemplating whether to do a hard reset on my device (iPad Air 2) but I'm afraid that won't solve my case even after doing so.

I encourage contacting Apple Support, however, it seems yours has been going on for quite some time now so I doubt anything would happen with mine as well.

But let's hope they'll fix these issues soon. I will try reaching out to them again, though.

I have just contacted them via Chat Support.

One advisor made me do this process: Settings>Wifi>Renew Lease, then try to sign in again but still did not work.

Now, their only supposed solution is to fully restore and do a factory reset like you did. Although, I'm very apprehensive about this step. Another advisor did confirm that nothing is blocking my device and account so that's good news.

Maybe it is a software bug after all and though I did raise this possibility as well, the team did not acknowledge it. I asked what would happen then if doing a restore and reset will still not work, the advisor just offered to use the services currently available in my area.

I have already talked to more than 10 advisors now on multiple support platforms and my issue that's been going on for almost a week now has still not been resolved.

In addition, I asked to confirm if the issue was not caused by the software update. The advisor then said that the issue may have been an underlying one already, and the update just exposes it, hence the issue timing. Doing a restore and reset would eliminate the possibilities of software issues, he said.

As for possibilities of hardware malfunction, he said there are still many variables that could have caused the problem. I have no idea how the hardware might have caused this problem though, I just don't see the correlation.