I have an old printer (Ortur-4) which I drive with a Compaq Presario V5000 (circa 2006). I use it once every few months, and it usually just works. A couple of weeks ago I wanted to do a quick print, but the power supply caused problems, and I noticed to the connector was bent. So I just unplugged the supply and tried to use the browser to do the print.
At that point the browser would not let me login to the Octoprint server. I tried a few things from various postings here, but none worked. Since the battery was about to die, I figured I could just purchase a new connector and then start the process of figuring out what was going wrong.
After waiting 2 days, I got the new connectors. But they were the wrong outside diameter. So much for a quick test print. I figured out the right part number and ordered again. 2 days later, I got the right connector. That gave me power to the laptop - and then my problems started.
I tried to upgrade octoprint, but this failed. Reading the install instructions it says I needed python 3.7 or higher. I had python 3.4. After trying a few things, I figured I'd just install a new Ubuntu because I have a DVD with 18.04 on it and the laptap has a DVD reader (it's old!) After 3 hours, I had a new version of Ubuntu on a new partition. That had python 3.6 - so still not good enough.
OK - fine! Just upgrade 18.04 to 20.04. After another 3 hours (and the next day) it said I have python 3.8. Great! I followed the instructions on the install page and finally got the octoprint server to run and the browser to find it.
But the connect button didn't work. Looking at the Terminal output, I realized the Auto serial port was not finding the correct port. Setting that manually, I then found the message "Connecting to serial port", but it never "Connected". So I downloaded minicom and started guessing what the baud rate might be.
After 10 tries, I just rebooted Ubuntu 14.04 and searched the files in Octoprint until I found the baud rate setting in config.yaml. I tried to connect to the printer again, but it would not let me login (which is where I started) so I rebooted back to 20.04. Manually setting the baud rate after starting the octoprint server got me connected to the printer and I could move the head using the Control section.
So now my old printer and old laptop are working again with the newest version of Octoprint. Hopefully the connector won't break and I can keep running this old stuff for a long time.