Unable to upload photos to posts or pages on WP 4.2.2

Hi. I’m brand new to blogging and WP and find myself totally stranded with this problem. I’ve set up WP 4.2.2 and using the Suits theme. I can upload photos to the library but not onto posts or pages or set up featured images. I’ve checked online and tried the following fixes but nothing works:

-Deactivating all plugins
-changing permissions from 755 to 777
-changing to 2015 theme then back
-uninstalling then reinstalling WordPress
-contacting my host to try fix it from their end

Nothing worked!

I’m a total beginner and know nothing about code so these past few days have been a real learning experience. I’m at my wits end now. Can anyone help? and please keep it all really simple. I don’t understand any of the jargon. Simple step-by-step ‘for dummies’ approach requested! Thanks!