I don't know why. The toolbar of waterGEMS is missing. How can I get it out?
Please follow the steps mentioned in below wiki to get the toolbar back, it also could be possible that this toolbar is docked to another area of application window.
Missing menu toolbar in standalone
Bentley Technical Suppport
The middle mouse button loses the function of the mobile model，how can solve it
Soounds like you have a problem with the drivers for your mouse. Try unplugging the mouse and plugging it back in or closing and opening the software. You might also want to try a restart of your computer if those don't work.