Not able to connect to PPP

Hi Team,

I am using EC200U-CN for connecting to network in PPP mode. Earlier the modem was working with Jio and sending data to server through MQTT. But after some months of operation, the modem is having PPP authentication issue. I am using ESP32 on other side to communicate with it. ESP-NETIF library is reporting “PPP authentication challenge” in debug and the PPP connection request is timing out. What could have changed in this, any leads? Here is the modem logs of some of the AT commands:

[2024-08-08_14:54:06:699]
[2024-08-08_14:54:06:699]Quectel

[2024-08-08_14:54:06:699]OK
[2024-08-08_14:54:07:734]
[2024-08-08_14:54:07:734]EC200U

[2024-08-08_14:54:07:734]OK
[2024-08-08_14:54:08:903]
[2024-08-08_14:54:08:903]EC200UCNAAR02A09M08

[2024-08-08_14:54:08:903]OK
[2024-08-08_14:54:09:623]
[2024-08-08_14:54:09:623]405854706018520

[2024-08-08_14:54:09:623]OK
[2024-08-08_14:54:10:262]
[2024-08-08_14:54:10:262]869523056892871

[2024-08-08_14:54:10:262]OK
[2024-08-08_14:54:10:884]
[2024-08-08_14:54:10:884]+CCID: 89918540507060185202

[2024-08-08_14:54:10:884]OK
[2024-08-08_14:54:11:538]
[2024-08-08_14:54:11:538]+CSQ: 17,99

[2024-08-08_14:54:11:538]OK
[2024-08-08_14:54:12:588]
[2024-08-08_14:54:12:588]+CREG: 0,1

[2024-08-08_14:54:12:588]OK
[2024-08-08_14:54:13:710]
[2024-08-08_14:54:13:710]+COPS: 0,0,"RJIO",7

[2024-08-08_14:54:13:710]OK
[2024-08-08_14:54:19:019]
[2024-08-08_14:54:19:019]+CGDCONT: 1,"IP","jiociot","0.0.0.0",0,0

[2024-08-08_14:54:19:040]OK
[2024-08-08_14:54:24:074]
[2024-08-08_14:54:24:074]+CGREG: 0,1

[2024-08-08_14:54:24:074]OK
[2024-08-08_14:54:28:195]
[2024-08-08_14:54:28:195]+QNWINFO: "TDD LTE","405854","LTE BAND 40",38750

[2024-08-08_14:54:28:195]OK
[2024-08-08_14:54:33:746]
[2024-08-08_14:54:33:746]+QENG: "servingcell","NOCONN","LTE","TDD",405,854,69E610,342,38750,40,5,5,6E,-111,-14,-78,39,16

[2024-08-08_14:54:33:746]OK
[2024-08-08_14:54:40:338]
[2024-08-08_14:54:40:338]+CFUN: 1

[2024-08-08_14:54:40:338]OK

Just from the log we don’t know why it is.
Which OS do you try the PPP?
Could you describe the network topology?
What if you do not try the MQTT and just run the PPP?