It is probably the update of MNE-Python that caused the problem, rather than the update of Brainstorm.
I updated Brainstorm to work with MNE-Python 1.0.3:
https://github.com/brainstorm-tools/brainstorm3/commit/8c886e24593692d89d0e322105ef11682888e7e1
I also updated the documentation for installing MNE-Python for Matlab:
https://neuroimage.usc.edu/brainstorm/MnePython
Please update Brainstorm and try again.