@tekbuff
An eBay rep posted a response on another discussion about this issue:
"There is a sitewide ticket open for sellers being unable to add tracking numbers. This is being worked on to be resolved and we do encourage sellers to reach out to customer support and have their account added to the ticket ALERT 15135. The more examples our Tech team has, the sooner they will be able to have this resolved. "
In the meantime, adding tracking using the app is working.
Options to contact CS: use chat on the left side of this page, entering agent in the chat box to get a live rep, or send a DM to one of eBay's social CS teams: ebayforbusiness on facebook, ebayforsellers on insta, askebay on X