Ryan,
Sorry to hear about the issues you are having. I have some suggestions below but want to first note that everyone in this forum, unless their profile specifically says "Google Employee", is a volunteer, even the Product Experts. As such, we do not have access to internal Google data or systems and are unable to directly help in some types of problems.
For your issue, generally the free storage offers I have seen are for a limited time (1 year, 3 years, 5 years, etc.) so it is likely that your offer has just expired. If you have any documentation showing that it should not expire you should contact Google support (information below) and provide that to them. The storage in these deals is purchased by the phone manufacturer and does not come directly from Google. When offers like this expire they do not delete any of your stuff but they do limit you to reading and deleting information. That is why yours says you are using 435% of your 15 GB quota. No new data (such as receiving emails) is allowed. This will continue until you have deleted enough information to be below your quota or until you purchase a larger quota.
If you do not have any documentation about this, it is likely that you will need to do something else such as sign up for Google One.
If you do have documentation or just want to try talking directly to Google's product support, you should be able to contact support from a link at the bottom of this page:
(There could also be a "contact us" button at the top right under your user image.)