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When going to Long term data > Query log, selecting the date and time range, you should see the queries for the selected date and time range.
Any queries that include “OK (forwarded)” result in “An unknown error occurred while loading the data”.
I have searched the forums but only found older posts regarding this error, and none of them seem match this situation. The interesting thing here is that it occurs only when “OK (forwarded)” is checked, if I uncheck this and leave the rest of them checked, then everything, eventually (depending on how many are left checked, I may have to tell the browser several times to wait for the script to complete, no big deal), works as expected.
It is also worth noting that it only takes from about 1 to 5 seconds for the error to appear, and the browser never prompts me to wait for or terminate the script.
Loving Pi-Hole BTW, the developers have done a great job, and it works very well in an enterprise environment.