Ever since updating to Octoprint v. 1.4.0 I can no longer get canceled prints to print again unless I restart Octoprint. Also, the connectivity in my home Windows network seems much slower. The camera takes longer to activate and is much more jerky. Uploaded files take longer to be ready to print and the white "Connecting to Octopirint..." screen takes much longer to load. I also started getting voltage errors that I hadn't seen prior to the update.
Could be some incompatible plugins. Try booting in safe mode and see if the problems persist. I've already heard a few problems with various plugins. Polar Cloud was causing a long cancel delay for at least one user, though I'm sure that will be fixed soon.
If you are getting the low voltage message then that power supply has an issue. Octoprint doesn't directly monitor the Pi voltage, it only reports the error when the Pi itself generates it.
What happens instead? I mean... what exactly are you trying to restart a print, which buttons are you clicking, and what does happen instead of the print starting again? What's going back in forth between OctoPrint and your printer - share a serial.log, enabled it first.
And as already said, voltage errors don't get reported by OctoPrint but the Pi, OctoPrint only makes them visible, fix your power supply situation, before that ain't fixed it doesn't make any sense to investigate further as everything else could be caused by your Pi browning out if it's not getting enough juice to run.
When a print fails due to bed adhesion, jammed filament, etc. I may need to cancel it and start over. The print will cancel fine but then the Print icon remains disabled unless I restart Octoprint. I used to be able to just refresh the browser to get the button reactivated.
In all versions including 1.4.0, the one with 2 will stay disabled since it's not actually "print this file" but "select and then print this file" - and what is already selected cannot be selected again and hence 2 will be deactivated for the already selected file up until 1.4.0. Since that's caused too much confusion though I've pushed a patch for 1.4.1 that will keep 2 enabled as well.
In general, when reporting issues, provide as many details as possible. That includes logs, version numbers, screenshots, possibly even videos of what you are seeing. It's impossible to analyse an issue if you have to pull every little detail from the reporter's nose
Your debugging skills are legend... I never even thought about that select and print button (and I even had the same misunderstanding about it as @Daviator). Brava!
