1)Can you attach the project?
2)Can you try connecting to a different BLE Central? Like mobile CySmart or something else and check if you face an issue?
I've attached our project to this comment. We've tried connecting using the CySmart App and the problem persists. Could you run our code and see if you experience the same issue? We notice that calling Cy_BLE_ProcessEvents inside the infinite for-loop fixes the issue but we are trying to minimize the number of times that Cy_BLE_ProcessEvents API gets called to conserve power.
Also during advertisement deep sleep alternates between successfully and failing to enter deep sleep mode. We are unsure if this is normal behavior because of the rapidity that deep sleep gets called.
DeepSleepMode02.cydsn.zip 11.7 MB