If use other PC. it does not have this problem.

Normally, the HDMI output port of PC will not equipped with HDCP. 

Since the HDCP protocol of Intel NUC11 cannot be disabled. 

If use this Inel NUC11 as the source PC, it is recommended to use its miniDP output with VC980/VC981 converter (miniDP to HDMI) instead of HDMI output.

reference: https://www.intel.com/content/www/us/en/support/articles/000058069/intel-nuc.html