Same problem - spent 30 minutes on a chat with eBay yesterday only to be told it's a technical issue at their end.  Tries again this morning and get the same error message - eBay say the issue hasn't yet been resolved.

Associates, Success finally at defeating the feared Sendle "Something turned out badly and we couldn't create the name"!! Notwithstanding the beneficiary's location being legitimate for Sendle, apparently your location as the source additionally must be substantial AND deliverable to by Sendle (I expect in the event that they need to return the thing as undeliverable). I was utilizing a PO Box as beginning for sending from and getting things. I have refreshed my Primary Address from the PO Box to my actual place of residence (My eBay > Account > Addresses > Return Address). I needed to do this for each of the 5 of the addresses I had in eBay (Registration Address, Postage Address, Dispatch Address, Return Address and Payment and Pickup). I was then ready to produce a Sendle Label. I'm presently during the time spent exchanging every one of my addresses back until I next need to create another Sendle Label. On account of sqleonhart who warned us about the Dispatch Address.

I had this problem too. I was able to make adjustments and print the label. Check that both the buyers address and your return address is in the correct format. In my case when I checked the buyers shipping details their ebay username came up on the first line of the the address block. My address had my old postcode which wasn't compatible with my new suburb. 

Once these were both corrected the label printing was possible. It seems most of these label printing errors are to do with buyer and sender addresses.

Hope this saves some people their sanity : )