serial uploading / SD card

Hi, I'm completely mystified I got a Feather ADALOGGER and it worked fine on blink, as I recall. I tried to load the example 'ReadWrite' and something changed. Now I can't upload to the board? I have a Metro also and it works fine on blink or whatever, but when I reconnect the Feather it sez 'problem uploading to board'. I think it may have uploaded something on the first try, because I put a little piece of blink in everything for an aliveness check, and that seems to be working but I can't upload anything else on top of it! Any help will be welcome.