Most likely, you just need to make sure that the current working directory is the directory which contains the QCAD binary and the various resources directories 'fonts', 'patterns', etc.
For more information about this problem, please refer to our FAQ at:
-> 11. I can't see any hatches / large texts / bitmap images.
-> 12. I can create dimensions but they show no label.
Note: it is strongly recommended to keep all files of the QCAD package in one directory (e.g. /opt/qcad/ or /home/user/qcad/, etc.). Spreading files around into various locations as it is commonly done under some Unix systems is not recommended since QCAD will not find its resources that way.