Unable to access ASRock Z170 Extreme 7+ motherboard boot menu using F11 key

ASRock Z170 Extreme 7+ MB
I've been using this mb for more than 18 months now with a variety of OSs (currently Win 10) and never encountered this problem until recently.

Unable to access the boot menu by pressing the F11 key. A rather weird screen displays (practically psychedelic in design with various colors) with the ASRock name/logo at the top of the screen. Nothing else.

Since we work with a number of installed drives - some of which contain different OSs - (we use removable HDD/SSD mobile racks configuration), we frequently have occasion to access the boot menu and the F11 process is a fine convenience compared with accessing the BIOS.

Latest BIOS update has been installed.

Raised this query with ASRock tech support but no response. Haven't as yet activated the CMOS button but thinking along those lines.

Would appreciate hearing from anyone who has run into this problem and if it was resolved.
 
Those keys access the BIOS. That I know. It's what I've been trying to avoid since it's a great convenience to simply access the boot menu upon bootup, especially since I work with a number of installed bootable drives.

I finally heard from ASRock in the meantime and they've concluded that the board is defective (after having been used without problems over nearly two years). They're in the process of issuing a RMA.

Anyway, thanks for your input.