Problems with nRF for Desktop and BL653 in DTM mode

In our product, we use Laird (Ezurio) BL653 BT module.
In some countries such product requires SRRC certification.
For SRRC certification we set BL653 to DTM mode with AT commands.
After switching BL653 to DTM we use nRF for Desktop to control radio signal.

Our product was SRRC certified few years ago. Now it requires renewal of the certification.
In the time of the original certification we were using nRF connect for Desktop V3.12.0 and Direct Test Mode V2.0.3
Now to prepare for SRRC renewal we tried latest nRF connect for Desktop V5.x but it is not able to communicate with the BL653.
The message is "cannot communicate with the device"
We also tried to install old V3.12.0 but it is not possible to install it now and we get message "Unable to retrieve source "official" from developer.nordicsemi.com ...". 

We need help how to use new nRF connect for Desktop V5.x with BL653 or how to install old V3.12.0 

Many Thanks,
Nenad

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