PSIsafe Web Troubleshooting: Full Text Search (FTS) fails to return results / does not function

PSIsafe Web Full Text Search Troubleshooting guide

Symptom #1:
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In PSIsafe Web. When performing a Text Search (Search/Text).
Processing spinner is displayed quickly and then goes away. No search results are displayed.

Errors in log file (in PSIsafe Web root folder/logs):
Error: System.Exception: Could not load file or assembly 'dtSearchNetApi4, Version=7.84.8405.39320, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified.
Cause: dtSearchNetApi4.dll is missing on server in the folder PSIsafeWeb/bin.

Solution:
#1: In IIS. Stop App Pool for PSIsafe Web.
#2: Place a copy of dtSearchNetApi4.dll in the PSIsafeWeb/bin folder. (version 7.84.8405.1 or later. Size ~603 KB).
#2: Start App Pool for PSIsafe Web

Symptom #2:
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PSIsafe Web does not display login page. Instead you get the following:
We are sorry. Application has experienced an error.......
Sign in again.

Errors in log file (in PSIsafe Web root folder/logs):
Error: System.IO.FileNotFoundException: Could not load file or assembly 'dtSearchNetApi4.dll' or one of its dependencies. The specified module could not be found
Cause: Dependency Microsoft C++ 2017 Redistributable (x86) version 14.11.25325 or later is missing on server.

Solution:
#1: Load Microsoft C++ 2015-2019 Redistributable (x86)
Note: Make sure you load the (x86) version.
Microsoft Download Link: https://aka.ms/vs/16/release/VC_redist.x86.exe
#2: Restart IIS.
#3: Restart PSIsafe 32-Bit Server Service. (called CNG-ServerService in 10.4 & 11.x)

Symptom #3:
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In PSIsafe Web. When performing a Text Search (Search/Text).
Processing spinner is displayed quickly and then goes away. No text search results are displayed.

Errors in log file (in PSIsafe Web root folder/logs):
Error: System.Exception: The type initializer for 'ApiInitializer' threw an exception. ---> System.Runtime.InteropServices.SEHException: External component has thrown an exception.
Cause: An unmanaged DLL dependency (dten600.dll) can be separated from the managed assembly when it executes. This occurs in ASP.NET applications when the application is copied to a temporary folder for execution. A DLL dependency of an assembly is not copied in this process.

Solution:
Register dten600.dll in the PSIsafe Web/bin folder.
#1: Open Command Prompt as Administrator.
#2: cd to the PSIsafeWeb/bin folder (where dten600.dll is located).
#3: Execute command: regsvr32 dten600.dll
#4: Restart App Pool for PSIsafe Web.

If none of the 3 remedies above resolves the issue do this:
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Clear temporary asp.net files.

#1: Stop IIS

#2: Go to C:\Windows\Microsoft.NET\Framework\v4.xxxxxxx\Temporary ASP.NET Files

#3: Delete the folders containing the name PSIsafeWeb in that folder.

#4: Start IIS.

Keywords: Full Text Search, PSIsafe Web, PSIsafe Web Full Text Search