Gmail Not Sending Messages Under ''alias''

I have a bit of an issue

i am running windows 7 home 64 bit sp1 on my pc but this happens in gmail whether its windows 8.1 or windows 10.

I have a gmail account i use for personal use, but i also have other emails i setup through hostgator for .com emails.
For convenience i setup my personal email to have my business emails to receive all the messages, and i could also pick within my personal gmail to ''send message as'' a specific email.

I keep getting this error message:
''Message not delivered
You're sending this from a different address or alias using the 'Send mail as' feature. The settings for your 'Send mail as' account are misconfigured or out of date. Check those settings and try resending.''

I checked my settings and they are correct , i also don't have any add ons in my gmail account.
Hostgator doesn't know how to fix this. I barely noticed this today when i was trying to send things through gmail

Seems this barely happened like a week ago or less because i was able to send messages fine roughly about a week ago. You would think that with a business email i would be sending more emails but the reality is i normally just get orders and send things ( i rarely have people message me about any issues or questions).


This is causing a bit of a slowdown, but i can still go to my hostgator panel , login through squirrelmail and send messages from there. I rather keep using gmail though as i have for the past couple of years

Any advice is appreciated