Probably easier to work through this with a Timer as there are fewer variables. Can you provide detail as to content of a specific group/scene that you cannot assign to a Timer? When the Group/Scene was established by EZSrve, did it say “Scene Saved Successfully” (meaning all the links had been successful). What is the Controller, what is the Responder(s)? I have many Groups/Scenes in my Insteon network and most cannot be controlled by a Timer. For example, SwitchLinc A is the Controller, LampLinc A and LampLinc B are the Responders. SwitchLinc A will have a “Controller of” link for LampLinc A and a “Controller of” link for LampLinc B. LampLinc A will have a “Responder to” link for SwitchLinc A and LampLinc B will have a “Responder to” link for SwitchLinc A. This Group/Scene can be defined by EZSrve, the links can be established by EZSrve, but the Group/Scene cannot be controlled by EZSrve. Nothing in the current Insteon architecture allows EZSrve, as a Controller, to operate this Group/Scene. Only SwitchLinc A can control this Group/Scene. Once we have a Group/Scene that can be controlled by an EZSrve Timer, then we can move on to a Macro. Someone in another thread made the comment that one has to think like an Insteon device when looking at Groups/Scenes and how they relate to Timers and Macros. I found this to be a helpful tip. Sorry if all of this is old news.
EDIT: Knowing the Unit (group) number of the scene that you created that cannot be assigned to a Timer is also important. The Unit number is stored in the Timer XML entry, where the Insteon device address would be for a specific device. I have found that Default_01 Group/Scene cannot be assigned to a Timer/Macro. If Unit 01 was used for your new group/scene, it could appear to be Default_01 and not be accepted.
EDIT2: I have created a Macro that triggers when X10 A06 ON, turning on Scene/Group SWineBottle and a second Macro that triggers when X10 A06 OFF, turning Scene/Group SWineBottle OFF. Scene/Group SWineBottle has EZSrve Unit 02 as Controller and a LampLinc as a responder. X10 A06 ON turns on the Lamplinc as a Group with a Group Broadcast, Group Cleanup Direct ON sequence and X10 A06 OFF turns off the Lamplinc as a Group with a Group Broadcast, Group Cleanup Direct OFF sequence. Image level is 1.52.