Flameshot and Ksnip

after last update 4 Weeks ago, Flameshot do not make any screenshots, no
error messages, nothing. Then I installed another Software “Ksnip” (same functionality as Flameshot) and same nothing, no
error messages.

KDE Plasma Version 6.02

ksnip is probably not updated for Plasma 6. KSnip fails to open/install after KDE 6 upgrade · Issue #1034 · ksnip/ksnip · GitHub

Flameshot works here on Arch (default Wayland).

You could use Spectacle, which is an official KDE app, constantly improved and better maintained.