error: Remote listing for winepak not available;

following 
https://github.com/winepak/winepak-sdk-images#instructions

doing 
flatpak --user remote-add --no-gpg-verify --if-not-exists winepak winepak-repo
results
error: Remote listing for winepak not available; server has no summary file. Check the URL passed to remote-add was valid.

clear linux. 
please advise