Power BI Report Server - Upgrade Error

Hi All

Recently I tried to upgrade Power BI Report Server from Sep'19 to Jan'20 but getting that following error:

Evaluation period has expired. Please upgrade to different edition before attempting to upgrade again.

Please help how I can resolve this as previously when I upgraded from May'19 to Sep'19 the process went smoothly but somehow got this error and right now I am unable to resolve it.