Experience Cloud: Guest Users Cannot Create Cases Using the Contact Support Button.

Field-level security (FLS) for the Web fields on the Case object needs to be updated for the Guest User profile to allow unauthenticated users to submit Cases from within Experience Cloud Sites.

In Lightning Experience

1. Click the gear icon, then Setup.
2. Go to Feature Settings | Digital Experiences | All Sites | Workspaces.
3. View the Guest Profile for the affected site.
   1. In Community Management: Manage | Community Management | Go to Force.com | Public Access Settings
   2. In Experience Workspaces: Workspaces | Administration | Pages | Go to Force.com | Public Access Settings
4. Scroll down to Field-Level Security.
5. Click the [View] link next to Case.
6. Click Edit on the next screen.
7. Enable Edit Access for the following 4 Web fields:
   1. Web Company
   2. Web Email
   3. Web Name
   4. Web Phone
8. Save changes.

In Salesforce Classic

1. Go to Setup | Customize | Digital Experiences | All Sites | Workspaces.
2. View the Guest Profile for the affected site.
   1. In Community Management: Manage | Community Management | Go to Force.com | Public Access Settings
   2. In Experience Workspaces: Workspaces | Administration | Pages | Go to Force.com | Public Access Settings
3. Scroll down to Field-Level Security.
4. Click the [View] link next to Case.
5. Click Edit on the next screen.
6. Set the following Web fields to Edit Access and save the changes:
   1. Web Company
   2. Web Email
   3. Web Name
   4. Web Phone
7. Save changes.

Once these changes are made, Cases should be created without issue.