since a few days ago, on one of my machines, the BOINC event log shows the following notice whenever it tries to fetch work:

27.11.2020 09:04:14 | GPUGRID | No tasks sent
27.11.2020 09:04:14 | GPUGRID | Tasks won't finish in time: BOINC runs 99.8% of the time; computation is enabled 100.0% of that

I never had that before; what does this mean? "Tasks won't finish in time" is impossible, since most of the tasks finish whithin one hour (being crunched with at GTX 980Ti)

Please, try taking a look to this thread: Only getting 1 GPU work at a time even though set for 10 days of work.
There it was discussed a similar strange notification.

Please, try taking a look to this thread: Only getting 1 GPU work at a time even though set for 10 days of work.
There it was discussed a similar strange notification.

thanks for the hint - problem solved :-)

Because of a problem with LHC which I run on that machine, too, a few days ago I had set the workbuffer to 6 days.
In the thread you referred to, it was advised to set this value to less than 5 days, which I did now. And since then, the GPUGRID tasks are being downloaded the way they did before :-)