Recently, I joined MLC with one of my PCs and successfully downloaded CPU and GPU tasks.
Today, I wanted to connect with another PC for crunching GPU tasks only (Geforce GTX970). I am sure that all the settings are correct, but whenever I want to fetch work (either automatically or manually via the Update button in the BOINC manager), the BOINC eventlog says:

24.04.2021 18:56:12 | MLC@Home | update requested by user
24.04.2021 18:56:12 | MLC@Home | Sending scheduler request: Requested by user.
24.04.2021 18:56:12 | MLC@Home | Requesting new tasks for NVIDIA GPU
24.04.2021 18:56:14 | MLC@Home | Scheduler request completed: got 0 new tasks

This excerpt has been made just now, however, I have been trying since a few hours.
The Server Status Page shows about 11.000 unsent GPU tasks - so I don't understand why I don't receive any. What could be wrong?

P.S.: No problem to download CPU tasks; but for this PC, I need GPU tasks only.

Hi Erich,

What version of CUDA do you have installed on that system? We need CUDA 10.2 or higher installed.

Hi Erich,
What version of CUDA do you have installed on that system? We need CUDA 10.2 or higher installed.

the NVIDIA Control Panel under Components says:
NVCUDA64.dll version 27.21.14.5671 NVIDIACUDA 11.1.96 driver

I now was curious and connected another PC to MLC, with exactly the same settings as for the machine I am referring here in this thread, i.e. download of GPU tasks not possible.

And to my surprise, this other PC could download GPU tasks. So the problem of not downloading tasks must have to do with - I don't know what. In fact, the CUDA version of the two machines is the same: NVIDIACUDA 11.1.96 driver. So the CUDA version is obviously not the culprit.
The PC which cannot download is described here: https://www.mlcathome.org/mlcathome/show_host_detail.php?hostid=11702

However, the other PC which can download GPU tasks cannot run them :-(
They error out a few seconds after they get started. Here you can see these erronous tasks: https://www.mlcathome.org/mlcathome/results.php?hostid=11741
The stderr says:

<core_client_version>7.6.33</core_client_version>
<![CDATA[
<message>
couldn't start app: Can't link app version file
</message>
]]>

the GPU inside is a GTX1650.
The description of this PC can be seen here: https://www.mlcathome.org/mlcathome/show_host_detail.php?hostid=11741

What does "couldn't start app: Can't link app version file" mean?

All in all, out of 3 machines on which I intended to crunch MLC, only one succeeds :-( This is sad, of course. Can anyone give me valuable hints for solving the various problems?

<core_client_version>7.6.33</core_client_version>
<![CDATA[
<message>
couldn't start app: Can't link app version file
</message>
]]>

the GPU inside is a GTX1650.
The description of this PC can be seen here: https://www.mlcathome.org/mlcathome/show_host_detail.php?hostid=11741

What does "couldn't start app: Can't link app version file" mean?

I suspected that above notice may mean that the BOINC version 7.6.33 was too old, so I updated to the latest one - 7.16.11.
Interestingly enough, a task got downloaded (as before), but it did not even start. So, the BOINC update brought no improvement.
One side-thought: how much RAM is required for a MLC GPU task? From what I see on the one machine where crunching works: the tasks take between 1 and 2.5 G of memory.
So could the reason why the task does not start be that there are only 4 GB RAM in the PC? Unfortunately, there is no way to inrease this.

I also updated the BOINC version on the other PC which does not even download MLC GPU tasks - however, no change. Still no tasks are being downloaded :-(
However, this machine also has only 4 GB RAM. So if the RAM requirement is higher, I would no longer have to worry about no tasks being downloaded.

One side-thought: how much RAM is required for a MLC GPU task?

I am crunching on a GTX 1650 Super under Win10. It is using 2148 MB of memory, according to BoincTasks.

One side-thought: how much RAM is required for a MLC GPU task?

I am crunching on a GTX 1650 Super under Win10. It is using 2148 MB of memory, according to BoincTasks.

and this obviously is too much for a 4 GB system.
Finally, the task which got downloaded and did not start right away, did start, but the system crashed after a few minutes. I rebooted and restartet the task, and again MemInfo showed an increasing need for RAM until the system crashed again.
This is really too bad, so I cannot crunch these tasks on two of my PCs :-(