Error "We’re unable to connect to your Microsoft Dynamics 365 server" when using Dynamics 365 App for Outlook

When attempting to use the Dynamics 365 App for Outlook, you receive the following message:

"We’re unable to connect to your Microsoft Dynamics 365 server. Please try closing and reopening the app."

If you click "Show more", you may see the following message:

"Client loader timeout"

If you use the app in Outlook Web Access (OWA), you may see the following prompt appear at the bottom of the screen:

"Do you want to allow dynamics.com to use additional storage on your computer?"

If you clear the Internet Explorer browser cache, this error may appear to be resovled but eventually returns.

Microsoft is aware of an issue where this error can occur because Internet Explorer is configured to limit the amount of data that can be cached. If you are viewing the app using Internet Explorer, this may be the cause of the error. If you encounter this error using Outlook Desktop, Outlook is always using Internet Explorer to display the app.

Microsoft is working on a change to avoid this issue. In the meantime, you can use the steps below as a potential workaround:

Option 1 - Increase database limit within Internet Explorer options

Depending on the version of your operating system, you may be able to change the limit within the settings of Internet Explorer. If you are using Windows 10, this option does not appear and you can use Option 2 instead. 

1. Open Internet Explorer.
2. In the upper-right corner, click the gear icon and then click Internet options.
3. On the General tab within the Browsing history section, click Settings. 
4. Click the Caches and databases tab. 
5. If you see an option "Notify me when a website cache or database exceeds" option, change the value to 200 and click OK. Alternatively, you can select dynamics.com from the list of websites and then click Exceed limit. If these options do not appear, continue to Option 2.
6. Clear the Internet Explorer history and cache. For detailed steps, see View and delete your browsing history in Internet Explorer. 

Option 2 - Increase the database limit within the registry

Important This section contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, see How to back up and restore the registry in Windows.

To increase the allowed caching limit, create the following registry entry:

To create this registry entry, follow these steps:

1. Click Start, click Run, type regedit, and then click OK.
2. Locate and then click the following registry subkey. If the path to this location does not exist, you may need to create the mentioned keys:
   HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Internet Explorer\BrowserStorage\IndexedDBValue
3. Right-click IndexedDBValue, point to New, and then click DWORD Value.
4. In the New Value #1 box, type MaxTrustedDomainLimitInMB, and then press ENTER.
5. Right-click MaxTrustedDomainLimitInMB, and then click Modify.
6. Click Decimal, type 200 and then click OK.
7. Quit Registry Editor, and then restart the computer.
8. Clear the Internet Explorer history and cache. For detailed steps, see View and delete your browsing history in Internet Explorer. 

There are multiple potential causes for this error. If this does not resolve the issue, refer to the following article for additional potential solutions:

https://support.microsoft.com/help/3124910