I have read what I think is all post on this and nothing seemed to be working. My excel option is grayed out on reports (except .csv option). This is not a new install and started happening suddenly. Everything was working fine.
QB's Premier 2017, Office 2010, Windows 10.
I tried changing user control to Don't Notify and restart. Didn't work.
I tried repairing Excel and restart. Didn't work.
I tried reinstalling both QB's and Office (and restart). Didn't work.
I tried repairing QB's and Excel. Didn't work. Not going to repeat restart, but yes restarted.
I tried verifying and rebuilding data. Didn't work.
I did a experiment with restarting the computer. I have been getting instances of Excel opening on restarts. If I open Qb's and access the reports, then Excel will open 1, sometimes 2 instances on restart. I don't open QB's then Excel won't open on restart. Not a computer expert, but this lead me to think there is a bug in QB's. Hate to think that QB's would try to force an upgrade by removing a feature - they have never done that before. :-|