Connection problem: LwM2M Server Internal Error 5.00

Hello,

I am using dynweb.data-worldwide.com.

I have registered the device (.csv file) and added protocol according to the manual: LWM2M - Cumulocity IoT Guides .

My device is trying to register to coap://lwm2m.cumulocity.com:5783, but gets response from Server: Internal server error 5.00.

The same situation is with:

coap://lwm2m-server.cumulocity.com:5783,

coap://3.64.138.218:5783.

The attempt to reach bootstrap server lwm2m-server.cumulocity.com:5683, was successful, but after redirection to lwm2m.cumulocity.com:5783, the connection can not be established due to server error as described above.

Still I can successfully communicate to other servers, like: try-anjay.avsystem.com, so I wonder if there is any problem on device side.

Please let me know any possible solutions as soon as possible.
Thanks in advance.