If you are seeing this error "The specified file 'Name of File' could not be uploaded. The file is an unsupported version or in a corrupt/malformed format. Please place an order for Family Finder or download the file and try again." it is likely you are trying to upload Version5 which is not supported by FTDNA. My suggestion would be to test again with Ancestry. You can then upload your Ancestry results to FTDNA and then take advantage of both databases of Ancestry and FTDNA. For your 23&Me results you might consider uploading them to Gedmatch using the Genesis Beta tool. You can then access your matches from their database.
There is an important new study out on human population genetics variation. The focus is Scotland and the Isles, but the data and analysis span all of Britain and Ireland. Read about the study, get the link to it, and see a key map at this recent blog - https://www.sprouls.org/post/massive-new-genetics-study-for-britain-and-ireland