Hi there, let us know which device you are using and firmware version of the device.
You may kindly follow the below steps:
As mentioned JIO SIM is working fine in 2nd slot, looks like the problem may not persist with the SIM slot but the SIM itself.
But again to check kindly put another SIM in 2nd slot and see if it works properly.
Kindly put the SIM in another device and see if the problem persists.
Kindly get in touch with the network provider.
. Last option would be to visit the service center to have a check. Locate here:
https://www.asus.com/in/support/Service-Center/India