EM7455, EM7421 unable to use CHAP


since September 2021 we are having connection issues with the following modem types: EM7455, EM7421

To be more specific they are apperently unable or unwilling to use CHAP as an authentication method.

EM7455 - it seems like 30% of our modems have this issue - the newer the device - the more likely the issue is.

EM7421 100% of our modems have this issue.

We are using Windows 10 Fujitsu Notebooks - drivers and firmware are up to date and the configuration of all notebooks is 100% identical.

The Notebook models are alle from Fujitsu: T938, U729, U759, U7510, U7511
In total we use roughly 1400 devices

Now to the interesting part: we can switch the modems and it will solve the problem → so we don’t think its an issue with windows, the configuration or the Software we use.

To be more specific, if we find a “working” EM7455, we can switch it with a “non working” one and it will fix the device. So it seems to be a Modem issue. They don’t seem to be deffective either, since they work with a different SIM (thats not using CHAP).

It feels like a change in some of the device, like a new revision of the hardware. This would explain why EM7421 won’t work at all. Futhermore oder model modems, do work at 100% - the EM7305 for example.

We tried different firmware versions, drivers and also different Windows Version - without any success.

I hope you have some suggestion or input.

Thank you very much for your time and feedback.

We will need logs etc. Please reach out to us via your support channel and we will surely help you.