Functionally the Mk2s is a more accurate Mk2. it has upgraded parts, in particular the smooth rods and the linear bearings. the Y axis bearings are held in place with U bolts instead of Cable ties.
the same slicer settings will work with either version.
Check you have the latest firmware and software/drivers loaded as appropriate.
when activating Slic3r, make sure you select Mk2 or Mk2s... NOT Mk2 Multimaterial or Mk2 Multimaterial single colour / filament...
Prusa control is a simplified user experience but it has not been updated for a while... (Quite a while)
Prusa intend to integrate Slic3r and Prusa control, but there is no published time line, that I am aware of.
If you have not used your printer for a while, it would be worth carefully scrubbing your PEI build surface, with dilute Dish soap/detergent and drying it with a clean paper towel. before you try to use it...
As you have probably moved the printer in that time, it's worth re doing your Live Z adjustment too (Use Jeff Jordan's 'Life adjust Z my way' version 6.1 files assembly-and-first-prints-troubleshooti ... ml#p119348
the files are at the bottom of the first post)