If you are having trouble posting on Facebook, try the following:
Make sure that you have the latest version of Adobe Flash. Most of the time this will fix any issues with adding photos to Facebook.
If you are having trouble tagging a business page, try posting through the computer instead of a mobile device
If you are having trouble posting on Instagram, try the following:
To tag someone in the photo, as you are uploading a photo, tap the "Tag People" button. Tap on the person or object in the photo you want to tag. Type in the username and it should appear from a drop-down menu
To tag someone is a photo caption, type @ and the username of the business