It appears that a bug has been introduced within the 26.4.x updates for Mac, iPhone and iPad that affects the Contacts / FaceTime Apps.
In brief, the issue is characterised by the Contacts App contact-cards, for Users known to use FaceTime, now being shown with the corresponding FaceTime video icon/button ghosted (i.e. unavailable).
At this time there appears to be a limited workaround. A FaceTime video call can be successfully made from within the FaceTime App - by tapping the green "New" button; this will open the New FaceTime dialogue. Here you can enter the target recipient's name within the "To" field - and then selecting the corresponding recipient from the candidate list. The FaceTime video call can then be initiated - demonstrating that the target recipient is (a) signed-in to the FaceTime service, and (b) can receive FaceTime calls.
Interestingly, the problem does not appear to be universally experienced by all users that have updated their devices. By example, my wife (having also updated her iPhone and iPad to the latest version) has not yet encountered the problem. Having checked, our individual device and App settings appear consistent between our devices. We obviously have different Apple Accounts and are signed-in to Apple services using our individual account credentials; of itself, this might suggest that the problem is in some way associated with the impacted User's Apple Account.
You and others that encounter this issue need to submit a Bug Report to Apple via its Product Feedback portal:
Feedback - Apple
You might be wise to submit multiple Bug Reports to Apple - one report each for the Contacts and FaceTime App - in addition to individual bug reports for each specific affected device (such as iPhone, iPad and Mac). In submitting multiple reports to Apple, you will hopefully reach the appropriate team. Drafting the body-text your Bug Report offline - and then using cut and paste - can usefully facilitate effective and quick submission of your bug reports without the hassle of trying to type the entire report multiple times.
Here's another discussion in the same vain:
FaceTime icons grayed out for some contac… - Apple Community
Every report counts - as until Apple receive a sufficient number or reports, it is perhaps unlikely that resources will be assigned to investigate and resolve the issue.
When submitting your Bug Report(s), please ensure that you include as much detail as possible within the body of the report - including your iPad model and installed version of the OS and the impacted Apps and Apple services; don’t rely upon the pick-list alone, as this rarely includes the full range of device models or most recent versions of macOS/iOS/iPadOS.
