Problem sending routes from BaseCamp to an iPhone 8+ to XT

A question from a Basecamp phobic user. XT and iMac.
I can see the device and even update it using Garmin Express. However, I am unable to load existing routes in Basecamp to the XT. My setup works fine with a NavIV, Oregon 700 and even Fenix 5X. I tried the single connection, etc. Am I missing something?
The routes I wish to load are both in Basecamp and on the NavIV (just in case there a Garmin to Garmin trick...) Many thanks.

I found this workaround from another forum which worked for me. Important: set up is XT and iPhone 8+ with Garmin Drive App.

Disconnect the Garmin from your computer
Export the routes from Basecamp to a location on your computer (desktop, specific folder, etc.)
Email the routes, one at a time to yourself (just to help you keep organized)
Open the email on your phone and open the attachment
Click on the Share button in the upper right hand corner (iPhone - not sure about android)
Scroll across the apps on the pop-up screen until you get to the three dots (...More) option
With your XT turned on, select Copy to Drive
The Drive App will open on your phone and ask if you want to transfer the file to your XT
Say yes, and it will transfer.

It is laborious but it works.
Oh, and if you cannot find the files on the XT after this, they are in Route Planner...

IMac will not send routes from BaseCamp to my XT

I hope this helps someone else struggling with this same issue.
I am still dumbfounded by the Basecamp to XT transfer not working whilst OK with other devices. I am sure some one will crack it eventually. Cheers
Thread closed

Case closed.