As has been discussed elsewhere [1][2], on some units of the USB Logic Analyzer (TOL-15033), the pin below CH6 is incorrectly labelled “GND”; the only actual ground pin on those units is the one below CH7.
The reason I’m posting is to report a new symptom of using the wrong pin.
When we first tried to use the logic analyzer, it only worked properly at a very low sampling rate (20-25 KHz). At any higher rate, the unit appeared to communicate properly with PulseView (i.e. the run lasted about the right amount of time, and the verbose log messages seemed reasonable), but there was no useful output. PulseView showed all the signals remaining HIGH throughout the run – even lines which we knew were busy.
When we switched to the correct GND pin, the unit began working correctly, up to its rated maximum speed of 24 MHz.
So if you see the device working only at rock-bottom sampling rate, this might be the cause.
[1] the warning on the product page, https://www.sparkfun.com/products/15033
[2] forum post viewtopic.php?p=224167#p224167 and its replies