Are the qt5 packages installed?
pamac list -i | grep "^qt5"
qt5-base 5.15.0-4 extra 67,2 MB
qt5-declarative 5.15.0-1 extra 25,9 MB
qt5-imageformats 5.15.0-1 extra 213,1 kB
qt5-location 5.15.0-1 extra 11,6 MB
qt5-multimedia 5.15.0-1 extra 3,7 MB
qt5-quickcontrols 5.15.0-1 extra 5,0 MB
qt5-sensors 5.15.0-1 extra 930,7 kB
qt5-styleplugins 5.0.0.20170311-23 community 1,2 MB
qt5-svg 5.15.0-1 extra 502,1 kB
qt5-tools 5.15.0-3 extra 17,1 MB
qt5-translations 5.15.0-1 extra 12,4 MB
qt5-wayland 5.15.0-1 extra 6,5 MB
qt5-webchannel 5.15.0-1 extra 228,2 kB
qt5-webengine 5.15.0-5 extra 151,8 MB
qt5-webkit 5.212.0alpha4-6 extra 49,0 MB
qt5-websockets 5.15.0-1 extra 309,4 kB
qt5-x11extras 5.15.0-1 extra 41,6 kB
qt5ct 1.1-1 community 815,1 kB