Did your collection location change at one point? There was a theory recently that this is behind what makes the app stop to showing the info. Same happened to me (I was changed from Bluewater to Staines also).
The person in question noted that when they called Tesla and had their original pickup location reinstated, the app started showing the timings again.
Either way; it appears to be nothing to worry about, just a bit more painful going via the site (especially if you have MFA turned on and have to go through that too fairly regularly! And…. you check the site for updates say, more than 10 times a day…
)