Cannot install any Office add-in — "We couldn't connect to the '{0}' catalog server" on Mac desktop and web

Question

I am unable to install any Office Store add-in. Every attempt fails with the error:

"Add-in error — We couldn't connect to the '{0}' catalog server for this add-in." (Note: the message literally shows the placeholder '{0}' instead of the catalog name.)

Environment:

• Personal Microsoft 365 subscription (no organization tenant, no admin, no group policies)
• macOS, Excel/Word/PowerPoint desktop apps — all affected
• Office on the web (office.com) — same error

The error occurs for ALL add-ins, not just one specific add-in (I originally tried to install "Claude by Anthropic for Excel").

Troubleshooting already done, with no effect:

• Cleared the Office add-in cache on Mac (Wef and Caches folders in the Excel container)
• Signed out and back in to my Microsoft account
• Enabled optional connected experiences in privacy settings
• Tested on a different network (mobile hotspot)
• Tested in different browsers (Safari, Chrome)
• Tested with multiple Microsoft accounts
• Updated Office via Microsoft AutoUpdate

Since the error is reproducible on every network, in every browser, on both desktop and web, and with multiple accounts, this appears to be a service-side issue with catalog/Office Store access, not a local configuration problem. Microsoft support chat (AI) was unable to help.

Is this a known issue, and can it be escalated to the Office Store / AppSource team? What can be checked on the service side for my account?I am unable to install any Office Store add-in. Every attempt fails with the error:

"Add-in error — We couldn't connect to the '{0}' catalog server for this add-in." (Note: the message literally shows the placeholder '{0}' instead of the catalog name.)

Environment:

• Personal Microsoft 365 subscription (no organization tenant, no admin, no group policies)
• macOS, Excel/Word/PowerPoint desktop apps — all affected
• Office on the web (office.com) — same error

The error occurs for ALL add-ins, not just one specific add-in (I originally tried to install "Claude by Anthropic for Excel").

Troubleshooting already done, with no effect:

• Cleared the Office add-in cache on Mac (Wef and Caches folders in the Excel container)
• Signed out and back in to my Microsoft account
• Enabled optional connected experiences in privacy settings
• Tested on a different network (mobile hotspot)
• Tested in different browsers (Safari, Chrome)
• Tested with multiple Microsoft accounts
• Updated Office via Microsoft AutoUpdate

Since the error is reproducible on every network, in every browser, on both desktop and web, and with multiple accounts, this appears to be a service-side issue with catalog/Office Store access, not a local configuration problem. Microsoft support chat (AI) was unable to help.

Is this a known issue, and can it be escalated to the Office Store / AppSource team? What can be checked on the service side for my account?

Answer 1

Hello Miloslav Maryško

Thank you for providing such detailed testing.

Based on the results, this does not appear to be caused by the Mac installation, browser cache, network, or one particular add-in. The important detail is that the Store opens and the add-in reaches the consent screen, but the catalog verification fails only after Allow and continue is selected.

Because it affects multiple Office applications, Office for the web, different networks, browsers, accounts, and add-ins, further local troubleshooting is unlikely to resolve it.

Please contact Microsoft Support for further assistance on this issue:

Please note that this is a user-to-user support forum. Moderators and contributors, including external Microsoft employees, are not allowed to directly interfere with Microsoft product features or access back-end systems. Our role is limited solely to providing technical guidance on reported incidents, requests, or ideas.  

1. Open a website link - Contact - Microsoft Support 
2. In the box below "We're here to help", type Microsoft 365, click "Get Help", and then click "Contact Support" below. 
3. In this section, you will need to sign in to your Microsoft account. 
4. Select "Microsoft 365 and Office" under Products & Services, select "Technical Support" as the category, and click to confirm 
5. You can select " Chat with a support agent in your web browser " to access the chat window. 

Include the following information when contacting support:

• Exact error text, including the literal '{0}' placeholder
• Date, time, and time zone of a recent failed attempt
• macOS and Office version numbers
• Affected applications and browsers
• Names of two or three tested add-ins
• Confirmation that the failure occurs after Allow** and **continue
• Confirmation that multiple accounts and networks were tested
• Screenshots or a short screen recording, with personal information removed

I hope you can get the support you need, have a nice day.