In your LAST version, you missed the LOW statement.
Code:
if but1=1 and rel2=0  then
         high rel1 
         pause 20
                          
         while but1=1
         call check
         wend
         pause 20
                                       
         while but1 = 0
         call check
         if rel1=0 then
            GOTO Btn1PressDone
;         pause 10
         endif
         wend
         LOW rel1

         while but1=1
         wend
         pause 20
endif
Btn1PressDone: