I researched the problem, but I couldn't find anything similar. In the KDE system tray, the Ktorrent and Pamac icons are missing. I haven't troubleshot the Pamac issue yet, but Ktorrent runs normally, and deleting ktorrentrc file brings the GUI back. When the window is closed, the problem reappears. Ktorrent is running, but the icons to bring up the GUI are missing. The problem must be with the system tray.

OS: Manjaro Linux x86_64
Kernel: 5.10.18-1-MANJARO
Uptime: 3 hours, 15 mins
Packages: 1544 (pacman), 6 (flatpak)
Shell: bash 5.1.0
Resolution: 3840x2160
DE: Plasma 5.21.1
WM: KWin
WM Theme: ChromeOS-dark
Theme: ChromeOSDark [Plasma], Breeze [GTK2/3]
Icons: crystal_remix-1.0 [Plasma], crystal_remix-1.0 [GTK2/3]
Terminal: konsole
Terminal Font: Noto Mono 10
CPU: AMD Ryzen 7 1700 (16) @ 3.000GHz
GPU: NVIDIA GeForce GT 1030
Memory: 6414MiB / 64315MiB