Buttons 'OK' and 'Cancel' disappear in 'Add application screen'
Open in PPA panel:
Home -> Infrastructure -> APS Applications -> My applications -> Add application -> Switch radio button to 'Select an app from Application Catalog'
Such behavior was confirmed as software issue #1799675, and will be fixed in future updates.
It observed when the number of applications from Application Catalog exceeded some value (according to the tests the number is about 396).
There are 2 possible workarounds:
The one proposed earlier is to use direct link
https://<ip>:8443/admin/app/uploadto add application.
The second one is to download several applications, so they are not being listed in the list of Available apps from Application Catalog (use tab button to get at non-displayed OK button and confirm downloading).