Did you persist the F_Count data either side of the reset? If not, if you dont disable f-count checks, the back end will see the count start again from zero and will assume a replay attack until the device has reached a count where it is larger than the last seen value - try disabling F_Count checks (not recommended long term for deployment - unless using ABP) to see if solves problem - then look at how to improve handling for deployment. Note: A successful OTAA join will reset count at both sides consecutively avoiding this problem, and is inherently more secure that ABP.
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