Extending Keil MDK 5.39 Community edition license after 5.40 changed the licensing process

I have Keil MDK 5.39 installed on my laptop. A few days ago, I noticed a message about the expiration date of the license coming soon. I do not intend to upgrade to MDK 5.4x yet as I'm trying to finish some work and I don't intend to waste time with installation issues for the moment. Last year I sent the PSN found on the download page and I forum and received the license ID code. However, this year the registration process has changed and it uses a license server. Some people here noticed problems activating the product (errors communicating with the server).

Question: how should I (re)activate my MDK (5.39) this year to keep it going for some time beyond the license expiration date without upgrading to 5.4x yet? Is it even possible?

I need to mention that I need to finish my project without changing tools for another 2 or 3 months. We are using the tools in university and I cannot break anything that works.

Thank you