A couple time a month, I receive the following email from my router:
Error notifications
Updater execution failed:
INFO:Target Turris OS: 7.0.1
ERROR:
runtime: [string “requests”]:451: [string “utils”]:441: Getting URI (https://repo.turris.cz/hbs/omnia/lists/foris.lua) failed: SSL connection timeout
line not found
line not found
line not found
Any ideas on how I can fix this?
Most likely temporary internet connection failure. What kind of access do you have?
Fiber. Usually the connection is pretty stable
Reflash your router of course 
Or provide more info. This is general connection error. So general advice is to do your homework and check at the moment or monitor your connection
Me for example I also have fiber that is pretty stable but yesterday evening between 22:00-00:00 quad9 (the DNS service I use had some outage). And it was not just me reporting that:
https://downdetector.com/status/quad9/
So even “there was internet” there “was no internet” so I changed the DNS to NIC.CZ ones for the night and everything was back operational