Hello @Anoop Chandran,
once a device connection string is established, you should be able to skip the DPS enrollment step.
Only when the IoT Hub denies access, accessing the DPS could be a plausible solution.
This will work for most DPS linking scenarios except for mobile devices, depending on the lowest latency.
This brings us to the unexpected behavior you experience.
In this scenario, I assume you use an individual enrollment based on symmetric keys.
You need to store the complete device connection string, looking like this:
HostName=[iot hub name].azure-devices.net;DeviceId=[device name];SharedAccessKey=[primary key]
The primary key could be the same as the one used for individual PDS enrollment.
The device name could differ from the registration name though.
Compare the connection string with the one seen in the portal to be sure:
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