Hmm... Did you make sure you resaved the file once you edited it?
Otherwise here is a more detailed guide
1. Once you have opened dnSpy, load up the HeatSDK.Core.dll file
2. Click the dropdown menus in this order
View attachment 3022906
3. Click on the options class
View attachment 3022913
4. Find the boolean variable "authenticated" (Mine says true, but uncracked it will say "false")
View attachment 3022915
5. Right click the line & hit "Edit Method"
View attachment 3022919
6. Change the value of "authenticated to true"
7. Hit compile, & then save the changes you made (I usually just close the program at this point, as it asks you to save it when you close it.
8. Enjoy your newly cracked Heat & feel free to share your SDKCore if no one else has uploaded it yet
P.S. You can also change other variables this way, so have fun experimenting!