A screenshot shows support at a glance what's happening on your screen. For error messages, it's best to always include one.
Windows
Press Windows key + Shift + S.
Drag with the mouse to select the area. The image is then on the clipboard.
Paste it into the email or ticket with Ctrl + V. To save or annotate it, click the notification in the bottom right.
macOS
Press ⌘ + Shift + 4 and drag to select the area. For the whole screen, press ⌘ + Shift + 3.
The image is saved on the desktop and can be dragged into the email from there.
Also hold Ctrl to copy the image straight to the clipboard and paste it with ⌘ + V.
Smartphone
iPhone: briefly press the side button and volume up at the same time.
Android: briefly press the power button and volume down at the same time.
Tip: Capture the whole error message and add when the error occurred and what you were doing. Cover passwords and confidential data first.