Microsoft 365 repeatedly fails on start up

This is a recently purchased machine.

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I am not the user of this machine, it belongs to the Tenbury Agricultural Society, a charity.  It is installed in their office, used twice a week for about 3 hours.

Every time it is powered up office 365 fails to load, timer icon just sits there spinning.  All Office 365 applications fail to load.   As far as I can ascertain it is powered down correctly.

I have run all the diagnostics software which gives a good result, done a clean re install of windows 11 and other software twice to no avail.   I have carried out the re-installs in my house.  As a test I have repeatedly powered the machine up and down and it works fine.  All that’s different is the power up and down is several days apart where it is installed and the location.  A  laptop running win 10 for example works fine on the same site.

Any clues as this is doing my head in.

By the way I can’t find a way of contacting Dell support.