Sitecore tree not loading for general link field

When I click on the "insert link" of the general link field, then the complete tree is not opened (as shown in the screenshot below), due to which I am not able to select the item.

When I checked the console of the browser then I noticed that the following API is giving 200 status but not returning the item in item[] (see screenshot above)

https://<mydomain>/-/item/v1/sitecore/shell?sc_itemid={11111111-1111-1111-1111-111111111111}&scope=c&sc_database=master&language=en&fields=__Hidden

I am not sure what is the fault?

I have tried the following:

1. Checked that item API is enabled
2. Logs have no clue regarding this issue
3. My project has no code where item API is extended.
4. All required templates and are present