Hi Rameez Arab,
1. What do you mean "detect", could the WSUS clients show up in WSUS server, could they report to WSUS server?
2. WSUS server 2012R2 use http port 8530 and https port 8531, we need to append the port to the WSUS URL, for example, WUServer
http://wsusserver:8530 , please check if you use the correct format;

3. If the WSUS URL is correct, while the issue still exits, please check if automatic update is enable, and reset SUSClientID:
Reset SusClientId on clients:
1). In cmd, net stop wuauserv
2). Delete the value in registry key " SusClientId " and "SusClientIDValidation" locates in:
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate
3). In cmd, net start wuauserv
wuauclt.exe /resetauthorization /detectnow
Welcome to feedback.
Best Regards,
Anne
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