When I opened my UE4.27.2 blueprint project in Ue5.32, the interfaces were all blank, but the function templates in them were in the places where I used them. I can’t edit or add any new functions. Has anyone seen this, and is there a solution? Thanks in advance.
Hey there @DiliupG! Generally it’s recommended to back a copy of the project up first, then upgrade projects one version at a time for the best odds of forward compatibility. It’s difficult to fix everything that can go wrong with upgrades. It’s likely that the classes are broken or corrupted.
HI! I have backups on storage and github. My question is why it happens and what is the solution. My project builds and runs as a packaged product on UE4.27.2. A copy of the same project opend in UE5.3.2, with the correct plugins added, never shows any Interfaces though all interface links run correctly. This apparently is a bug. Any solution other than to re do the interfaces which is a nightmare? 
When updating it straight to 5.3.2 it likely breaks too much to do much else than rewrite them. I would still recommend upgrading one version at a time to pinpoint where the breaks occur, and it may be easier to circumvent them inside the process.
Opened the project in UE5.4.4 also gives the same error but packaging and build works with no errors. Interfaces, though not visible in the respective bluprints work without a problem and can be added to new blueprints and used without any problem. Just reporting back for anyone who is interested.