activation issue-NortonUtil v15

I purchased NUv15 with 3 PC key. The 3 PC's activate correctly initially BUT at various times weekly each become de-activated.

When I try to reactivate each of them again they USUALLY re-activate w/o a problem, but sometimes they tell me my key is invalid and to contact support. Support has been unsuccessful in any resolution via voice call or email. They use LOGMEIN remote access and they activate it but it NEVER stays activated, I am very frustrated- is there any solution for me short of asking for a refund?

 

[using Win7 HomePrem, NIS 2011, 4G ram, 500G HD, HP Pav dm4-1173cl- w/core-i5]

 

Thanks for any help/suggestions!