"Something went wrong. Please try again." Error When Adding Image to Account Engagement Lightning Enhanced Email/Landing Page Builder

To resolve this issue, you would need to use a CMS Channel and CMS Workspace for the Email Builder which is not using the 'enhanced' options. The steps to do this would be as follows:

1. Click the Digital Experiences Home action menu, select CMS Channel, choose a Public Channel, and then click Next (Using a public channel ensures that you can delete the Account Engagement package in the future.).
2. Name your channel and click Next
3. Ensure the 'Enable Domain' toggle is set to on and that a domain is selected for the CMS Channel. Click Next. 
4. Enable the "Use non-enhanced APIs" setting. Click Next and Done. 
5. Click the Digital Experiences Home action menu, select CMS Workspace, and then click Add Workspace.
6. There are two CMS Workspace types of 'CMS Workspace' and 'Enhanced CMS Workspace'. Select the 'CMS Workspace' option. Enter a name for the CMS Workspace and then select 'next'.
   1. If you do not see the option for "CMS Workspace", go to Setup > Digital Experiences > Salesforce CMS and make sure the "Create both CMS workspaces and enhanced CMS workspaces" setting is enabled
7. Add the CMS Channel configured in steps 2-3 above to the CMS Workspace on the 'Add Channels' step of the CMS Workspace creation.
8. Select the default language for the CMS Workspace and click 'Finish'. You can then select the Salesforce users that need access to the workspace, and then select a role for each (A content manager has full access to a workspace’s files. A content admin can also edit the workspace settings).
9. On the 'Content Setup' page in the Salesforce Admin Setup menu, for step 3b with the CMS Channel, change the CMS Channel to the one created in the steps above which is not an enhanced CMS Channel. Save the change.

Once a CMS Channel which has "Use non-enhanced APIs" enabled is selected in Content Setup, when you add images from CMS in either the the 'Email Template' builder or the current email builder experience in 'Email Content' or Landing Page Builder, the image should display and work as expected without any error message displaying. The images may need to be republished. 

To Note - As part of the Spring '24 release, there is a 'New email experience' option that can be selected with the Email Content builder. In this optional email editing experience, user's will get to looks at some of the next-gen features with the existing user-experience. The CMS Channel/Workspace this new email experience option uses is with an 'enhanced' CMS Channel/Workspace. On the backend, it is currently hardcoded to reference a newly created pre-made enhanced CMS Channel/Workspace which as a result, will mean you will see a default enhanced CMS Channel named 'Account Engagement Content Space Channel' and CMS Workspace named 'Content Workspace for Marketing Cloud Account Engagement Enhanced'. These cannot be used with the current email experience in Email Content, the Email Template builder or the landing page builder as they don't support it. Which means, on the Content Setup page, you should not select 'Account Engagement Content Space Channel' as the CMS Channel