Disabled access to Excel MS Store or offline installation

Due to policy in some companies, individual user cannot install apps from MS Store.

You can see for example message like this

Sorry, Microsoft 365 has been configured to prevent individual acquisition of Office add-ins

https://answers.microsoft.com/en-us/msoffice/forum/msoffice_word-mso_mac-mso_365hp/office-add-ins-prevented-by-365/e01f07df-618e-4ce7-acf3-cde0973f04da

We do not support not authorized installation, however with help from your administrators you can still install apps in alternative way.

Admin Center / SharePoint App Catalog

Preferred way by using Admin Center - https://docs.microsoft.com/en-us/office/dev/add-ins/publish/centralized-deployment
Using SharePoint App Catalog - https://docs.microsoft.com/en-us/office/dev/add-ins/publish/publish-task-pane-and-content-add-ins-to-an-add-in-catalog (which have few flaws like: disabled commands, no Mac support and in hybrid ecosystem Admin Center is advised to be used).

Offline installation

Unfortunately, for Office Store (unlike for example on a Windows 10 apps Marketplace) there is no way to have completely offline installation (beside development mode – sideloading, which shall not be used for production environments)