What is the problem?
Never ever ever been able to connect; always get the 'unable to connect'.
Octoprint / Mini Delta wouldn't work- but I now have the solution and want to put it here
What did you already try to solve it?
Everything google has ever said.
Solution was found here: CR-10 Connection ERROR 2308 (hook GPX)
"Disable GPX".
Once I did that- everything worked.
Logs (octoprint.log, serial.log or output on terminal tab, browser error console ...)
Additional information about your setup (OctoPrint version, OctoPi version, printer, firmware, browser, operating system, ...)