Many people have noticed that Forge doesn't embed the metadata in the pictures in a way that CivitAI can digest, which results in posts missing the checkpoints - and not being crosspossted to the checkpoints pages as a result.
After some lurking, I've found a reddit thread, that had a guy who had figured it out.
I'll copy what he said here for posterity:
Must fix webui\modules\hashes.py
Turns out in 2024-08-11 they changed the method of hashing and replaced function 'calculate_sha256' into 'forge_fake_calculate_sha256', and renamed 'calculate_sha256' into 'calculate_sha256_real' Which resulted in the difference of the hash.
So, simply go to line 63 and replace 'forge_fake_calculate_sha256' into 'calculate_sha256_real'.
Since the 'sha246' function looks for cache first, you'd better also remove files from webui\cache\hashes, otherwise the function will keep returning the wrong hash.
I've tested it myself, it works fine enough. Although I'm using Stability Matrix, so every time it tries to update something (I don't know what it updates in Forge >.>), the hashes file also resets, so I have to re-edit it every time.