---
title: "Troubleshooting installation errors"
slug: "troubleshooting-installation-errors"
abstract: ""
---
# Troubleshooting installation errors

At the end of an on-prem installation, one of the following error messages might appear. Follow the instructions to correct the error.

<details>
<summary><h2>Could not load file or assembly 'System.Diagnostics.DiagnosticSource'</h2></summary>

If you get the *Could not load file or assembly 'System.Diagnostics.DiagnosticSource, Version=4.0.2.0'* exception:

1. In the `web.config` file, add the following *bindingRedirect* tag:

    ```xml
    <dependentAssembly>
        <assemblyIdentity name="System.Diagnostics.DiagnosticSource"
            publicKeyToken="cc7b13ffcd2ddd51"
            culture="neutral"/>
        <bindingRedirect oldVersion="0.0.0.0-4.0.2.1" newVersion="4.0.2.1"/>
    </dependentAssembly>
    ```

2. Run the installation again.

</details>

<details>
<summary><h2>Could not load file or assembly 'Microsoft.IdentityModel.Clients.ActiveDirectory'</h2></summary>

If you get the *Could not load file or assembly 'Microsoft.IdentityModel.Clients.ActiveDirectory'* exception:

1. In the `web.config` file, check that the following bindings exist:

    <dependentAssembly> <assemblyIdentity name="Microsoft.IdentityModel.Clients.ActiveDirectory" publicKeyToken="31bf3856ad364e35" culture="neutral" xmlns="urn:schemas-microsoft-com:asm.v1" /> <bindingRedirect oldVersion="0.0.0.0-3.19.3.10102" newVersion="3.17.2.31801" xmlns="urn:schemas-microsoft-com:asm.v1" /> </dependentAssembly> <dependentAssembly> <assemblyIdentity name="Microsoft.IdentityModel.Clients.ActiveDirectory.Platform" publicKeyToken="31bf3856ad364e35" culture="neutral" xmlns="urn:schemas-microsoft-com:asm.v1" /> <bindingRedirect oldVersion="0.0.0.0-3.19.3.10102" newVersion="3.17.2.31801" xmlns="urn:schemas-microsoft-com:asm.v1" /> </dependentAssembly>

2. Add any missing bindings to the `web.config` file.
3. Run the installation again.

</details>

<details>
<summary><h2>Could not load file or assembly 'Polly'</h2></summary>

If you get the *Could not load file or assembly 'Polly'* exception:

- Read [this KB article](https://kb.sitecore.net/articles/237210) to resolve the issue.

</details>

<details>
<summary><h2>Could not load file or assembly ‘Microsoft.Extensions.Caching.Abstractions' or ‘Microsoft.Extensions.Caching.Memory’</h2></summary>

If you get the "*Could not load file or assembly‘Microsoft.Extensions.Caching.Abstractions' or ‘Microsoft.Extensions.Caching.Memory’* exception:

1. In the `web.config` file, verify that the following bindings exist:

    ```xml
    <dependentAssembly>
    	<assemblyIdentity
    		name="Microsoft.Extensions.Caching.Abstractions"
    		publicKeyToken="adb9793829ddae60"
    		culture="neutral"/>
    	<bindingRedirect
    		oldVersion="0.0.0.0-3.1.5.0"
    		newVersion="3.1.5.0"/>
    </dependentAssembly>
    <dependentAssembly>
    	<assemblyIdentity
    		name="Microsoft.Extensions.Caching.Memory"
    		publicKeyToken="adb9793829ddae60"
    		culture="neutral"/>
    	<bindingRedirect
    		oldVersion="0.0.0.0-3.1.5.0"
    		newVersion="3.1.5.0"/>
    </dependentAssembly>
    ```

2. If any of the bindings are missing, add them to the `web.config` file, and run the installation again.
3. Check if the `bin` folder contains the `Microsoft.Extensions.Caching.Abstractions.dll` file. If it does not, download the correct version of the file from `[https://www.nuget.org](https://www.nuget.org)`, and paste it into the `bin` folder.

</details>