You will see the message:
VocAlign Project could not do
if you try to use the AU (ARA) Version of any Synchro Arts plugin in Logic Pro 10.4.8.
This is because Logic Pro 10.4.8 does not support ARA operation.
ARA operation requires Logic Pro 10.5.1 or higher.
For improved ARA performance, we recommend Logic Pro 10.6.1 or higher.