Timer not triggered

I have a timer process, where the timer configured as following:

Timer condition is a environment constant, and we a switch in UI where user can change the constants value from false to true or from true to false, to decide whether they want the timer process run

It has been working fine, but today when I  turn on the switch, which mean I changed the value of the constant from false to true, the timer process is not triggered

Can anyone advise?