Your descriptions are quite confusing. Could you please elaborate more clearly:

-   Are you saying in your post that you run a MobiControl web console on a TAB which itself is a device being managed by MobiControl?

- What is the platform/mode/firmware-version of your TAB?   What platform(s) of device(s) have you tried but failed to enrol ?  What enrollment method have you used?     

- Is your MobiControl server on-premises and residing in a closed network covered by your restricted Wifi network ?  Is your device management address set in MCadmin.exe a private or public IP/FQDN?  What about the "primary agent address"?

- What is the version and build numbers of your MobiControl server?

Hi Thanks for the reply.

Yes, To check and confirm, came out from the Lock dowm mode & checked in Google chrome.

Samsung Galaxy Tab A -> T285 Android 5.1.1 , Enroll the device by enrollment id

Samsung SM-T116IR Galaxy Tab IR  -> Android 5.1.1, Enroll the device by enrollment id

Samsung SM-T116NY ->  Android 4.4.4, Enroll the device by enrollment id

13.4.0.5003

It is cloud server, SAAS.  Most of my client using the Open network (SIM Card) . One of my clinets is using the TAB by SOTI MDM on the restricted WIFI. Primmary management server is S006514.mobicontrolcloud.com Port:5494

How many devices (including the TAB running web-console) have been successfully enrolled since the very initial deployment?   Are  they of the same brand/model/firmware version as you showed in your reply?  Were they enrolled using the same Add-Devices Rule as your current list of devices with enrollment problem?

Did Soti support make any network configuration changes on the cloud-based server for you? Have you tried adding a brand new add-devices rule and re-try your device enrollment?

What port(s) did you open in your Wifi network for Soti service at mc-enroll.soti.net ?

What did you see on the device screen after entering the enrollment ID? Could you show device screenshot(s) or device log (where you see "Connected to server failed")? 

Did you see any prompt/message on the device screen about Samsung ELM licenses?   Your restricted Wifi network should have firewall exceptions for KNOX servers.  Which part of the world (America, Europe, Asia, Africa, etc.) are your Soti cloud server and Restricted Wifi network located?