I upgraded from 8.1.xx to newest version and all my tags dropped out from one of my tag sections. Wondering if this has happened before. I updated my other 3 ignitions gateways easily without this issue happening. I hit restore backup to see if the back up would bring the tags back in but it did not.
I have not seen this before, and I know this is not super helpful for this case as you already upgraded. General rule of thumb I use before upgrading anything is to take a backup file of anything at risk [ie, gateway backup and designer / tag export]. This could at least allow you to easily recover if something happens to the tags during the upgrade.
Confirm it didn't just drop your default tag provider. If it has the wrong tag provider selected it might look like you don't have any tags.
Is it a redundant system?
Edit:
I worded that badly...
If the default tag provider configured on your project changed it would look like your tags are gone.
Confirm tag providers are enabled. When a tag provider is disabled none of the associated tags are available.
I did have an occurrence with an earlier version of 8.1.x where it appeared my tags were gone. A gateway restart resolved it and I have not seen that occur since.
I have had several times when Ignition appears to behave anomalously even when configuration seems right and gateway restart usually resolves that too.