Frames not received nor transmitted on external clock

Hi folks, in my setup I have connected external clocks (with or without tsync). The SYS_TIME register keeps updating (with active tsync only to the value when sync pulse is received). However I am not able to transmit or receive single packet. The diag led near dw1000 is blinking and radio seems to be configured as normally. Do anybody has a suggestion what I could be missing?