I tried that (btw, by uninstalling the plugin, you mean to put the openHAB plugin on the inactive list and then reboot?).
I did it, reactivate the plugin, tried to install openHAB clicking the button but nothing changed. Same messages as before. Still no openHAB server active.
Please let me know if I can try something else.
My Max2Play installation is quite old, but I updated regularly and so I did today.