Can't assign macro to mouse button: Requires Synapse

I confirm I've observed this same behavior with my Razer Deathadder Essential mouse, with Razer Synapse installed (version 3.6.1201.111814). I tried mapping the 4th and 5th buttons to Windows functions Copy and Paste, which appear in Razer Synapse with the red warning label and the same message, "Razer Synapse must be running to use this function". I'm guessing there could be some kind of interprocess communication problem preventing an API from responding, since the application is already running.

I've opened a ticket with Razer Support, case # 211203-004739. After reinstalling with a clean upgraded Windows and running Synapse as administrator with a support account, the same issue repeated. I'm waiting to hear from the next higher team. I hope the developers come up with some better messaging for this condition, since running Synapse to be told that Synapse needs to be running leaves me nonplussed.

I'm working with Senior support now, having confirmed for their satisfaction this is a problem I really experienced. They've told me that the red icon signifies no problem at all, that "the red icon on Synapse does not mean that it is not able to set a configuration on the button, you can still use that mapping and it will work as long as Synapse is active." Which still seems like poor UX, but whatever... Except that my configured functions are still not working as expected. I don't know what macro OP had chosen, but I'd chosen Copy and Paste. Instead of copying and pasting text as I press the buttons, the letters C and V are output instead. I understand that Ctrl-C and Ctrl-V are commonly used in Windows to execute copy and paste in most applications, but that's not been happening.

I have the same problem now with my Basilisk x Hyperspeed mouse. I also see the same "Synapse needs to be running..." error after configuring but upon testing, the functions I assigned still work. Hope they can fix this as it's really confusing, especially for new users like me.