ReadTrialState() not working anter "MYAPP -enterkey"

I have workbook in trial state with nag screen on. It shows 7 days left.
When I try to check it with ReadTrialState it shows 0 instead of 7 days.

ReadTrialState works only with first activation key.
After reentering new key with “MYAPP -enterkey” counter is reset to 0. Why? What is wrong ?