Visual Studio Community 2017 version 15.9.2 unable to load symbols from the Microsoft symbol server

I am using Visual Studio Community 2017 version 15.9.2 and I am trying to debug something in C#. I wanted to load symbols but my symbol cache is totally empty despite me having configured Visual Studio correctly.

When I explicitly load symbols for the Unity.Mvc.dll assembly that I am interested in by selecting Load Symbols from the Modules pane while debugging, it attempts the download ultimately displaying Cannot find or open the PDB file. in the Symbol Status window.

The Symbol Load Information dialog reports as follows.

C:\Program Files (x86)\IIS Express\Unity.Mvc.pdb: Cannot find or open the PDB file. C:\Users\computer\AppData\Local\Temp\Temporary ASP.NET Files\vs\385c2246\beb904df\assembly\dl3\91f61dc3\00610fa0_6b3fd401\Unity.Mvc.pdb: Cannot find or open the PDB file. C:\projects\aspnet-mvc\src\obj\Release\net45\Unity.Mvc.pdb: Cannot find or open the PDB file. C:\Windows\Unity.Mvc.pdb: Cannot find or open the PDB file. C:\Windows\symbols\dll\Unity.Mvc.pdb: Cannot find or open the PDB file. C:\Windows\dll\Unity.Mvc.pdb: Cannot find or open the PDB file. C:\Users\computer\AppData\Local\Temp\SymbolCache\Unity.Mvc.pdb\41297c5a10a2446ba7397343f3dbad86ffffffff\Unity.Mvc.pdb: Cannot find or open the PDB file. C:\Users\computer\AppData\Local\Temp\SymbolCache\MicrosoftPublicSymbols\Unity.Mvc.pdb\41297c5a10a2446ba7397343f3dbad86ffffffff\Unity.Mvc.pdb: Cannot find or open the PDB file. C:\Users\computer\AppData\Local\Temp\SymbolCache\Unity.Mvc.pdb\41297c5a10a2446ba7397343f3dbad861\Unity.Mvc.pdb: Cannot find or open the PDB file. C:\Users\computer\AppData\Local\Temp\SymbolCache\MicrosoftPublicSymbols\Unity.Mvc.pdb\41297c5a10a2446ba7397343f3dbad861\Unity.Mvc.pdb: Cannot find or open the PDB file. C:\Sathyaish\repos\private\sathyaish.net\Code\Unity.Mvc.pdb: Cannot find or open the PDB file. SYMSRV:  BYINDEX: 0x3
         C:\Users\computer\AppData\Local\Temp\SymbolCache*https://msdl.microsoft.com/download/symbols
         Unity.Mvc.pdb
         41297C5A10A2446BA7397343F3DBAD86ffffffff SYMSRV:  UNC: C:\Users\computer\AppData\Local\Temp\SymbolCache\Unity.Mvc.pdb\41297C5A10A2446BA7397343F3DBAD86ffffffff\Unity.Mvc.pdb
- path not found SYMSRV:  UNC: C:\Users\computer\AppData\Local\Temp\SymbolCache\Unity.Mvc.pdb\41297C5A10A2446BA7397343F3DBAD86ffffffff\Unity.Mvc.pd_
- path not found SYMSRV:  UNC: C:\Users\computer\AppData\Local\Temp\SymbolCache\Unity.Mvc.pdb\41297C5A10A2446BA7397343F3DBAD86ffffffff\file.ptr
- path not found SYMSRV:  HTTPGET: /download/symbols/Unity.Mvc.pdb/41297C5A10A2446BA7397343F3DBAD86ffffffff/Unity.Mvc.pdb SYMSRV:  HttpQueryInfo: 80190194 - HTTP_STATUS_NOT_FOUND SYMSRV:  HTTPGET: /download/symbols/Unity.Mvc.pdb/41297C5A10A2446BA7397343F3DBAD86ffffffff/Unity.Mvc.pd_ SYMSRV:  HttpQueryInfo: 80190194 - HTTP_STATUS_NOT_FOUND SYMSRV:  HTTPGET: /download/symbols/Unity.Mvc.pdb/41297C5A10A2446BA7397343F3DBAD86ffffffff/file.ptr SYMSRV:  HttpQueryInfo: 80190194 - HTTP_STATUS_NOT_FOUND SYMSRV:  RESULT: 0x80190194 SYMSRV:  BYINDEX: 0x4
         C:\Users\computer\AppData\Local\Temp\SymbolCache*https://msdl.microsoft.com/download/symbols
         Unity.Mvc.pdb
         41297C5A10A2446BA7397343F3DBAD861 SYMSRV:  UNC: C:\Users\computer\AppData\Local\Temp\SymbolCache\Unity.Mvc.pdb\41297C5A10A2446BA7397343F3DBAD861\Unity.Mvc.pdb
- path not found SYMSRV:  UNC: C:\Users\computer\AppData\Local\Temp\SymbolCache\Unity.Mvc.pdb\41297C5A10A2446BA7397343F3DBAD861\Unity.Mvc.pd_
- path not found SYMSRV:  UNC: C:\Users\computer\AppData\Local\Temp\SymbolCache\Unity.Mvc.pdb\41297C5A10A2446BA7397343F3DBAD861\file.ptr
- path not found SYMSRV:  HTTPGET: /download/symbols/Unity.Mvc.pdb/41297C5A10A2446BA7397343F3DBAD861/Unity.Mvc.pdb SYMSRV:  HttpQueryInfo: 80190194 - HTTP_STATUS_NOT_FOUND SYMSRV:  HTTPGET: /download/symbols/Unity.Mvc.pdb/41297C5A10A2446BA7397343F3DBAD861/Unity.Mvc.pd_ SYMSRV:  HttpQueryInfo: 80190194 - HTTP_STATUS_NOT_FOUND SYMSRV:  HTTPGET: /download/symbols/Unity.Mvc.pdb/41297C5A10A2446BA7397343F3DBAD861/file.ptr SYMSRV:  HttpQueryInfo: 80190194 - HTTP_STATUS_NOT_FOUND SYMSRV:  RESULT: 0x80190194 https://msdl.microsoft.com/download/symbols: Symbols not found on symbol server.

This isn't the first time this is happening. I usually solve this one every few years and forget how I did it.