@Žajdlík JosefI believe I've found a reason for your issues and they are solved in Beta ... you confirmed it, perfect.
In Pro, login most probably expired and usually, it is automatically restored, but because of your issue, it does not work anymore. Sorry for this, Beta needed

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@balloni55not clear from UI, I know, but the top panel with "Login required" is not clickable. It is the same as in Pro version > just information panel. Login is automatically called at the moment, you use the function that needs a login, like load of PQ files.
Anyway even here, you see only "loading", hmm. In which browser login opens? Or you see a browser with the same blue top panel as is in Locus (and "Powered by Chrome" visible under top right three-dot menu)?