Unfortunately, eBay do not come to these boards, but you are not alone as some are also reporting not being able to leave feedback.
It could well be a device or browser issue, if you are on the app or mobile browser switch if you can to a PC / laptop and use Chrome, seems to be less issues with that combination.
Feedback is entirely voluntary and you do have 60 days in which to leave some, if you wish.
@sd56-10
