In addition it looks like Proton guys are not interested really in supporting any third parties access:
There is plenty of Proton Drive related issues on this forum we can’t do anything about. @henrybear327 did fantastic job with reverse engineering their API but without anybody else able to carry on ongoing maintenance this remote experience apparent software rot. IMO it should be marked as unsupported at the moment. It will save a lot of frustrations and time wasted by users. Unfortunately its current designation as beta creates false impression that it is pretty much working - which is no longer the case.