[Not a valid template] and other errors

– WordPress up to date? 4.6.1
– NextGEN up to date? 2.1.50
– NextGen PRO up to date? 2.3.53
– All plugins up to date? Yes
– Do you have a caching plugin installed? No
– Try disabling all browser extensions/plugins and clear browser cache and reload, does that help? No

(please confirm the following, with your server host tech) :
– MySQL up to date (at least 5.6+)? :No, 5.1.55 is the latest the host provides
– PHP up to date (at least 5.6+)?: No, 5.3.6 is the latest the host provides
– The mod_rewrite Apache module activated? n/a
– PHP Safe Mode OFF? n/a

Additional information that will help us find a solution:
– Who are you hosted with? Aabaco Small Business (Formerly Yahoo Hosting)
– What theme are you running? Generate Press
– Have you tried checking for a plugin/theme conflict as outlined above^ ? Yes. Everything worked perfectly until migrating to another host
– Does the issue occur in all browsers IE/Firefox/Chrome/Safari ? Yes

Please provide as much detail as possible and steps to reproduce the issue you’re seeing. Screenshots are very helpful and a link to the page on your site where the issue is shown.

The website that I’m developing is https://danrtalley.com. I tested it on my own host (bluehost) and have since transfered the WordPress over to my customer’s host (Aabaco Small Business formerly Yahoo Hosting). Aabaco hosting is extremely outdated and I’m trying to avoid switching his hosting provider right now because he has an exhibition coming up soon that I don’t want to be playing around with his website too much before hand.

Since I’ve migrated the hosting over to Aabaco, I’ve had a few problems with NextGen
– Unable to use the add gallery button in the post editor (the link is broken): https://prnt.sc/cyp5hh
– Unable to edit posts at all
– Unable to access the plugin options
– Imagely says it has 20 updates and if i click to install it freezes: https://prnt.sc/cyp58
– I get [Not a valid template] on every page that has a NextGen gallery: https://prnt.sc/cyp601
– I also have paid for the PRO upgrade which is up-to-date.
– I used the NextGen Reset Plugin to reset options

Do you have any suggestions? The only way I can even edit my posts is if I disable the plugin, otherwise the editor does not work.