Why can't I download mms messages?

I have an HTC One M8 unlocked. I've had the phone for about a week and noticed when sent a group message or picture text that it requires a download. Sometimes it starts download on its own and others I have to choose download or decline. After a download starts, about a minute after, it prompts me to make the same choice without my message being displayed. I also get a message it my drop down saying "generic network failure". This occurs both on WiFi and mobile data. I have Cricket wireless as my provider.

Welcome to Android Central! Is your mobile data otherwise working normally? Check your APN settings: https://www.cricketwireless.com/supp...n-android.html

I looked and the APN is incorrect however the only thing I can edit is the APN. I cannot edit the other settings and there is no option to add a new one.

What if you tap Menu on that screen? See this article for more info: What is an APN, and how do I change it? | Android Central

The only option is reset default. It appears that the firmware version I have eliminated the New APN option. I don't know if I can fix that.

If you happen to be on T-Mobile its more likely your provider and not the phone its self.
I have a Note 3 and M8 with TMO and from time to time a picture message will fail to down load. Its on their end not yours.

I only get reset default. I've read something about the firmware version I have having taken that option out but my wife has the same version on her phone and she can add new to hers. I don't know if I can fix this.

I have noticed that if I am on WiFi, my MMS messages will not download, however if I turn WiFi off they download fine.