Webdav is afgesloten

Running NC 15.0.2
Ubuntu 18.04
Apache

Today we were confronted with a sudden stop in syncing from our mobile devices to the nextcloud server.
The mobile tries to, but for every upload the message ‘webdav afgesloten. Proberen afgesloten bron te benaderen.’
Translation: ‘webdav closed. Trying to reach closed source’

I cannot find this error message in the documentation or the internet and I do not know what it means, or how to solve it.
The issue happening on multiple mobiles makes me think of th NC server, syncing from the desktop goes smoothely.
So I’m puzzled.
Can someone give directions how to solve it?

Many thanks in advance.
Kind regards
R. Bode

Sorry to hear you’re facing problems :slightly_frowning_face:

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