Thank you guys. Sorry, but the solution wit RBZ doesn't say anything to me. The other one with deleting the webcache file not working. In the meantime I get answer from Sketchup support. I guess I will wait until Monday and ask for local admin user and password. Than I will be able to install newest version of sketchup.
Once again thank you for your time.

Hello.
I have a problem with extension manager. I would like to use SimLab OBJ importer. I've bought already, but than the problem has apeared. When I try to open it a blanc window appears. When I try to open Extension Warehouse an information appears that Extension Warehous jas been disabled in my version of Sketchup (2021 PRO). I think the best solution would be to reinstall Sketchup, but I working on company computer and I must have local admin user and password. I've applyied for it , but didn't get answer yet. What is intresting when I click ,,check for updates'' button an information appears that there was a problem checking for updates, check internet connection.
Can anyone know the solution?