Need assistance to get Highend Theme back to working correctly.

Been a long day.

After the upgrade – initially looked ok but then realized could not access wp-admin.

Worked with both Host Gator and then Mojo support team to try and get it functioning.

Ended up rolling back to older version and while at first it looked like it was working – many php errors were occurring.

So worked with Hostgator again and they ended up uninstalling and then reinstalling – and the new version was reinstalled and back to the issue that I cannot access wp-admin to edit or update the site.

Hostgator is recommending to use a different theme! I really do not want to do this.

Hostgator mentioned that the new Highend theme is not compatible with the new version of wordpress.

Please advise asap or assist with what to do.

thank you.