Issue with importing Garageband projects & files

Collabing on a music project with someone out of state and having issues with their files. The GB Projects they send say they can't be opened bc they're "only compatible with Garageband for IOS" (tried in both GB and Logic Pro). And when they sent me the track as an MP3, I dragged& dropped, and the key + tempo changed from the parameters we'd set so it's unusable. Both Macs are up to date. Any thoughts would be most appreciated. Thx