OMG, this is a further website blocked. initiative-integral.org
Now the message is:
First I uploaded a fresh downloaded file of wpmudev-updates: no result.
Then I uploaded a fresh upfront-builder plugin.
Then I deleted the upfront file hat was in themes. (I made a copy before taking it down.
All did not work.
Please support, yet I get a bit crazy of this happening again and again to websites that have not been updated for a while.