I have tried moving the taskbar to the left side and I still experience this problem. I have also tried moving it to the top, rebooting, moving it back to the bottom and rebooting but I am still experiencing the problem. I wasn't experiencing the problem until a few days ago. It's possible my company pushed an update to Windows 10. I don't always know when that happens.
I my case, the taskbar might pop up once when a window is covering the bottom of the screen but then it is always behind any window that covers the bottom of the screen. I am running with multiple monitors, a laptop with 2 external monitors, and this happens on ALL screens.
I have encountered this problem in the past and it was usually fixed by bringing up the taskbar, either with the Windows key or using an uncovered part of the screen and clicking on the taskbar. That usually moved the taskbar to the front, even after it hid.
As a developer, this is extremely frustrating since I like to have access to my entire screen real-estate