Can you launch terminal and run
sudo nano /etc/systemd/logind.conf
Arrow key down to the line
#HandleLidSwitch=suspend
Change this in both of two ways: remove the hashtag # and change suspend to ignore:
HandleLidSwitch=ignore
Tap ctl+o to overwrite, then tap enter to save current configuration. Tap ctl+x to exit the editor.
Reboot... and test. Please relay the results.