My laptop has been running 24/7 for several months now running ARP on WCG using Linux Mint 19.3 & Boinc v7.9.3.
I normally check it once a day to see how it's doing.
Around 11:30 this morning on checking, see that the Boinc icon is missing from the taskbar so restarted it.
Not long after, I kept getting a dialogue box stating the following:
The Boinc client has exited unexpected 3 times within the last 3 minutes. Would you like to restart it again?

Of course, I clicked yes. same occurred within a short time. After numerous attempts, thought it could be an issue with the wireless connection so made connection a wired one.
Numerous Boinc restarts & computer restarts have all failed to get Boinc running.
Noticed another issue while doing all this, Boinc no longer auto starts on boot up.
Is this an O/S or Boinc issue?

Things usually break

a) when you change something
b) when they get old and overheat

When did you last upgrade either Linux or BOINC? Did you hoover out the dust bunnies while you were investigating?

A: Nothing changed.
B: Understood. Last cleaned last weekend. Shut it down once a month for a good clean.

Linux upgraded? No just all software updates installed & up to date according to its reports. Did try several times to upgrade Boinc but kept getting told that it was up to date (As far as I know 7.9.3 is all that is available in the repo).

Looks like it was option B after all. Laptop fan cutting out on start. So it's a case of ordering a replacement fan if available (laptop 9 years old next week) or get new one.