Newly setup WSUS all clients stuck at downloading 0%

Recently I created a newly WSUS setup for the first time and it's all still new to me so be gentle ;-) I've set up WSUS as described on the internet (pretty basic) and all went well without any problems; I then deployed all new Windows 10 Pro v2004 images via MDT to our office PC's (they were still running Windows 7 Pro): During the TaskSequence, I let the Windows machines update via the standard online Windows Updates services, then, as one of the last steps in the TaskSequence, I set the WSUS setting via PowerShell [below] on the clients (since I have to access AD, I cannot set it globally v

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