I was able to fix the issue!! It wasn't anything to actually do with the Operating System but it was AT&T itself! So basically you may not even have noticed this but if you go to Settings and General at the bottom is Restart ATT Backup & Sync service. Click that and OK and minute later a popup says Sync messages and you do so and it retrieves most of your messages and its a temporary fix however i found the permanent one. That though is what is causing the issues especially for MMS messages and especially ones coming from Iphones. You probably started the service without realizing. For example if you factory reset your phone or updated to new OS it asks you to sync and i guarantee most people didnt realize it was a free add on serivce they were pushing out. So AT&T pushed out this free service on your plan that backs up and syncs your messages in their cloud then pushes to your phone. This is so you can apparently read your text messages on a computer and even text from a computer. What seems to be happening is it is erroring or getting stuck in syncing in the cloud and never reaching the phone. IF you go to the website and log into your account then go to change or manage plan/services. You will see the free service at $0/month. Remove that service from your plan and confirm removal. BOOM!! My wife and I both have the HTC ONE M8 and this solved the issue and havent had trouble at all since!!