Pro Tools licensing is an Avid created mess, and the stupidity with subscriptions apparently supporting the latest version is well just not understandable. What numbat though that would be a good idea? Avid can't even copy what Adobe does and get it right... and yes an Adobe Creative Cloud subscription lets you get and run old stuff. This is all especially worse when combined with Avid not offering a way for users to upgrade old perpetual licenses.
The sensible advice may be to give up on Avid and Pro Tools and switch to Reaper or Logic Pro. Both immensely wonderful DAWs with often an order of magnitude less cost, less licensing games, and less overall hassle.
But I'm guessing that's not a practical option here. Avid had a promotional update program for folks with lapse update plans (or who never had one) but that ended December 31st. This promotional program:
https://www.pro-tools-expert.com/hom...until-31st-dec What I would do is call a sales rep at Vintage King (my preference by far) or Sweetwater and see if they still have any of these upgrade promotional upgrade things to sell you. Try to make sure you're talking to somebody who really knows what they are talking about, if not ask to speak to a Pro Tools licensing expert.
You may also have the option of purchasing a used perpetual license with current update plan, folks here on DUC are advertising them now, but make sure you are buying from somebody who looks reputable/is known here.