My microsoft surface no longer compatible with lightroom classic

The last version of LR Classic that supported Windows 8.1 was LR 7.  Unfortunately, Adobe doesn't make LR 7 available for download and I don't know of anywhere else you can download it.  Adobe tech support should have known that -- shame on them.

But are you sure you had LR Classic, which required a monthly subscription?  Perhaps you had LR 6 or earlier, which you purchased outright with a one-time payment? You can download LR 6 from here:

https://community.adobe.com/t5/lightroom-classic/update-lightroom-6-0-to-6-14/m-p/10819370#M170107 

But you will only be able to use it if you have a LR 6 serial number saved away (or it may be available in your Adobe account):

https://helpx.adobe.com/download-install/kb/find-serial-number.html 

[Use the blue reply button under the first post to ensure replies sort properly.]