Hi,
Sounds like another module is getting in the way of Min Purchase.

Suggest a *full module conflict test*:

To track down a module conflict, please follow these steps ** PRECISELY **:
(1) Install and activate a maintenance mode plugin (if desired)
(2) Then, DO ALL (*at the same time*):
(-) do a full site backup!
(-) deactivate ***all*** plugins except Woo, my plugin (and maintenance mode plugin)
(-) ** switch to a clean default theme like 2019 **
— (This removes all other possible conflicts.)
(-) turn off all deals except the one we are examining.

(3) ** test **
(4) if good, add 1 module back in. ** Retest **
(5) Repeat until conflict identified.

** This test depends on following the outlined steps fully. **

Best,
Vark

(PS – If you do have a module conflict, it will likely boil down to choosing between the 2 conflicting modules…)