I cannot read a .vtp file I could open yesterday. Can someone try to open it?

ParaView Support
20

Yes, exactly so: https://gitlab.kitware.com/paraview/common-superbuild/-/commit/6744ee3df360a374ec66f0793def67b379aca8c3

expat 2.6.0 came out just about a month before ParaView 5.12.0.