Upgraded Server Package & Now I Can't Add New Posts of Photos

My site was on old hardware on my server so I switched it over to a newer package for the same price. It should have only been two hours of downtime, but the site was down for 12 hours and when it came back I got huge errors. I can no longer upload new photos or new posts. When I go to add a new post there is strange text after the URL.

My server looked into this and found nothing wrong on their end. They claim it’s an error with WordPress. I don’t know what to do. Not being able to add new posts to a blog is a huge issue. Please let me know if you are able to fix this.