No available data elements in Program validation rule management

Dear DHIS2 team,

I try to test program validation rule in https://play.dhis2.org/demo.
Unfortunately, I could not find any available data elements in box
Available data elements (See below figure and attached gif screen recorder
for more details).

[image: Inline image 1][image: Inline image 2]

Could anybody tell me why there is no available data elements in Program
Validation Rule? It is not only in play demo server even in my own test
server the same thing happen.

Thanks and regards,
Rady