Static HTML file; error message, "This type of file can't be edited in Pinegrow"?

I’m an occasional PG user and haven’t touched it in about a year. I let my one-time license lapse.
A search of the forum (native and Google) proves fruitless.

I’m trying to open an HTML file that was not created in Pinegrow. How do I fix it?

Does it have a .html extension? Not really sure what else would cause this.

Thanks for your reply. Yes, it does have an HTML extension. Would it matter which OS it was registered under? I was using Linux when I first purchased it and a new laptop has NVIDIA graphics and Killer Wi-Fi–so I’m doing a term in Windows hell. Pinegrow Windows accepts my license code so it appears to be fine.

If you feel comfortable sending me the file/giving access I can check it out. The OS shouldn’t matter.

I had this exact issue when I first installed PG. The page I was trying to open had some antiquated code I had to get rid of - I don’t recall exactly but it might have been Spry-related, and then PG was able to open it. Anyway I believe this was corrected in later updates, I haven’t had this trouble recently.