This error could happen during running DbSync, deploying a package (LCS or manually) or just starting up IIS. Error message looks like the following:
Serialization version mismatch detect, make sure the runtime dlls are in sync with the deployed metadata. Version of file '204'. Version of dll '203'.
Versions could vary, but the file version is always higher then dll version.
The root cause of the issue is that your D365FO version is lower then the minimum version required by installed ISV solution as a binary model.
There are two possible solutions:
- Delete binary model
- Update D365FO to the minimum version required by ISV solution
