The $9.99/month subscription is for Pro Tools Artist, which was released with version 2022.4, when they introduced the new tiers of Ultimate, Studio, Artist, & Intro.
The last supported version of Pro Tools that ran on High Sierra was 2020.12. So, no, Pro Tools Artist will not run on High Sierra and that license won't authorize any version that will run on High Sierra.
The Pro Tools Studio subscription for $29.99/month is the equivalent to the previous version called Pro Tools Standard, and that license should authorize versions back to 12.6, one of which will definitely run on High Sierra.
Hope that helps.
Also, I have included a couple links, one to the Pro Tools Compatibility Chart which lists which operating systems each version is supported with, and one to the release history, which lists the different releases and which features they included.
Compatibility:
https://avid.secure.force.com/pkb/ar...tibility-Chart
Release History:
https://avid.secure.force.com/pkb/articles/faq/en393795