Hey there skippy.
It’s difficult to tell right away what could’ve caused this, did you previously have additional storage purchased with your subscription?
Can you confirm if it’s indeed your Data or your Assets that are over the allotted storage space?
For Data storage we would need to check to see what is taking up all that space, please see this document on how to check and delete unwanted files in your Data storage How to delete content from your data storage.
Do you see anything unusually large in your Data storage?
If your Asset storage is the problem, we have a different document to address this Managing storage on The Forge - Your Asset and Data Library.
With this you should be able to manage your storage and reduce it to manageable size, if anything is left unclear do let us know.