Hopefully Léonie will swing through here,
I heard my name, HangTime 🙂
SignorBass,
could you please check the download status in Mainstage2?
Launch Mainstage2 and open once more the "Download Additional Contents" panel from the main menu bar: "Mainstage > Download Additional Contents"
Look at the "Status" Column - does it say "Installed" for all JamPacks you want to use? If not, download and install again.
If it says installed, open the System Library and check, if the folders are there.
From your Systemdrive "Macintosh HD" open the folder "Library", then "Audio" > "Apple Loops" > "Apple"
You should see all five JamPacks there. The JamPack 4 Symphony Orchestra should contain 2203 items.
If the loops are installed, but GarageBand does not show them, reindex the loops. Simply drag the folder " JamPack 4 Symphony Orchestra" with the missing loops onto the Loop Browser in GarageBand.
Regards
Léonie