A project has been processed as a text file and is now corrupted


Sometimes the following error can appear when loading a project :

[Hdf5Archive] Archive 'project.spp' appears to have been processed as a text file and is irremediably corrupted.
[Project management] The selected project 'project.spp' isn't valid!

This error means the project has been modified outside of Substance Painter and cannot be read back properly.
It usually happens when a versioning software (such as Perforce) processed the Substance Painter project as a text file instead of a binary file. The only solution is to add a new rule/exception to the versioning software to force the processing of spp files as binary. For more information with Perforce, see the dedicated documentation : https://www.perforce.com/perforce/r16.1/manuals/cmdref/p4_typemap.html