iTunes, Mac, 645M: Garmin Express stuck on "Loading Music"

I have the same problem. I see no response as yet from Garmin or anyone with a fix. Have you had any joy ?
I'll leave mine on the loading music and let you know if I eventually get anything.

I've had a long email back-and-forth with Garmin employees who don't seem to have any clue about the problem. It took them 4 communications from me to even suggest anything that might be relevant (total uninstall and reinstall of Garmin Express, which did nothing to help). They get back to me every couple of days but I wouldn't be too confident of them coming up with anything. Either there's a serious bug in GE that requires fixing or, more likely, it's just very badly designed and requires a total rethink.

So I'm no closer to understanding what the problem is in Garmin Express or why it can't load my iTunes library. The behaviour is always the same: it shows "Loading Music" with a spinning wheel. If I launch Activity Monitor while this is going on, the RAM usage of GE starts climbing until it takes up all of the 8GB on my mac. At that point, it starts writing 1GB swapfiles to /var/vm at a rate of about 1 per minute and will keep doing so (I assume) until the computer itself is totally dysfunctional.

In the meantime, I've discovered a couple of workarounds. The 645M (and probably the other watches that can play music) use MTP (Media Transfer Protocol) for communications with the computer. Windows machines can mount an MTP device like the Forerunner as a USB drive but Macs cannot do so natively. There are, nevertheless, at least 3 ways that you can either mount the watch as a USB drive on a mac or at least have access to its filesystem. All have drawbacks but they will allow you to manually copy music files, podcasts, audiobooks, etc. to your watch.

1. The easiest (in terms of setup and cost) is to download and install Android File Transfer. It's free. This allows you to view the file system and add and delete folders or files. It does not, however, mount the watch as a USB storage device on your desktop.

The 645M (and probably the other Garmin watches with music) store those files in the "Media" partition. Click "Media" at the top of the window for your watch and you'll see something like the attached image. You can put audiobooks in the "Audiobooks" folder and podcasts in the "Podcasts" folder. For Music, I think you have to add a "Music" folder (without quotation marks). Within that folder, folders should be nested as follows: Artist/Album/Tracks (where Artist is replaced by the artist name, etc.).

2. Easier still (but costing money) is the Expert version of SyncMate. It costs $40 and does lots of other things—mostly for Android phones—that I don't really need, given that I don't have an Android phone. I haven't paid it so can't report directly, but I understand it will mount the Media partition on the mac's desktop to allow you to add and delete content from the device in the Finder. It will also automatically sync a folder in your mac with a folder on the watch, which could be handy for automating the process in a way similar to what Garmin Express is supposed to be doing. $40 is steep, though, especially since you've already paid several hundred dollars or the equivalent for a watch with music functionality. You can read more about it here. Also: you'll have to unmount the watch using SyncMate if you want to use Garmin Express to sync other non-music information.

3. Slightly more involved for the setup but free is to install simple-mtpfs on your mac. This basically lets you mount devices that use the MTP protocol as though they were ordinary USB storage devices. The setup is more involved because it's got a lot of pre-requisites and you'd want to be comfortable using the Terminal app to install things via the command line. First, you have to have Fuse for macOS installed. You also need to install the xcode command-line tools and then the Homebrew package manager (allows Linux-like installation of packages). Instructions on doing this can be found here. I did it and was able to mount the watch in macOS, but the terminal mount command gave me a "PTP Layer Error 2002" even though the device did mount on the desktop. I gather that this solution does a better job with such devices, but you have to compile it to install and I haven't yet bothered.

Anyway, I hope this helps others in some way. If anyone finds other solutions (or is able to better test these ones), please post more here.ciq.forums.garmin.com/.../1441633.jpg