It may be necessary to warm up the hole section of the part a little bit in order to properly get the screw in, I suggest using a heat gun at 170°C - 200°C and around 50% airflow for about 30 seconds before forcing the screw in.
If you don't have access to a heat gun you might also try printing the test file several times while trying different scaling options until you find what fits your printer's capabilities (use “Thread sample.stl”).
The author remixed this model.
Identical to the original design and dimensions, just added a threaded hole to screw it onto a standard ¼" tripod.