When Excel 365 starts it checks for linked data types on the MS servers and shows what’s available. That happens whether you’re using Linked Data Types or not.
If no response, that entire block in the Data ribbon doesn’t appear.
It seems there was a problem when the latest version of Excel tried to contact ‘home’ for data types information.
We’ve seen this problem before but as a Microsoft server problem. Linked Data Types (LDT) are serviced from various Microsoft server farms around the globe, Excel picks the closest one for it’s LDT connection. Very rarely, the nearest server isn’t working and Stock/Geo don’t show up in Excel.
The workaround is to use a VPN connection to somewhere far away from your real location then restart Excel 365 (either the USA or Europe should be more reliable). That should force Excel to check a different Microsoft server system,
Whatever happened (no announcement from Microsoft) it’s not a good look for Office’s much hyped cloud services or the way they are presented in Excel.
The decision to have Data Types disappear entirely when there’s no server connection is questionable. Better for ‘Data Types’ to appear but be blank or the Stock and Geography types be greyed out. At least the customer knows the feature exists though not currently available. That would be consistent with other Office ribbons where unavailable buttons are greyed out not removed entirely.