Evening erections

Hi all, can get erections in the morning fine now after many weeks of using the app, however evenings… at most I can only get a semi. Been with my wife for 12 years now and nothings changed between us feeling or sexually, it’s bringing us apart as my wife thinks it’s a ā€˜her’ problem when it’s not. I do work 12 hour shifts but I’m not tired or not wanting it or anything. Has anyone else ever experienced this?