Hi @abarton,
2018 versions are out of support for the educational program which covers the 4 most recent versions (currently 2022,2021,2020,2019).
The only option is to move to a newer version.
I agree with Leo. Only past 4 Versions are Available on Autodesk Website for Renewal Purposes.
Do you have any specific reason to not switch to a Newer Version..? Or are you just Enquiring..?