Maybe I just wrote the CSV files wrong....
Here is (as an example) the content of file "BoltSizes.csv" (based on plugin documentation): is the format correct?
Bolt Index,Bolt Size,D [in],N [Threads/in],Dpitch [in],Dminor [in]
1,2,0.086,64,0.0759,0.0691
2,4,0.112,48,0.0985,0.0894
3,6,0.138,40,0.1218,0.1109
4,8,0.164,36,0.146,0.1339
5,10,0.19,32,0.1697,0.1562
6,1/4,0.25,28,0.2268,0.2113
7,5/16,0.3125,24,0.2854,0.2674
8,3/8,0.375,24,0.3479,0.3299
9,7/16,0.4375,20,0.405,0.3834
10,1/2,0.5,20,0.4675,0.4459
11,9/16,0.5625,18,0.5264,0.5024
12,5/8,0.625,18,0.5889,0.5649