Here's what I do using PC & V4.32 it may be similar in mac.
In Inventoria go to 'Options' and select 'Web Access' and place a check mark next to 'Allow access to Inventoria on the
local network & click OK.
Now go to Express invoice,
Options, 'Inventoria, place a check mark next to -
'Allow express invoice invoicing software to synchronize with inventoria'.
Have you created an 'Access authentication code? if not create one example -
1234 make sure your IP address/ Port Number 1097 and the location name is all here, i.e. Main Warehouse. keep this page open.
You can check your locations by going into Inventoria, and look at your stock locations make sure these have the same name i.e. or the default name 'Main Warehouse'
go to Inventoria-options and then 'Other'
place a check mark next to 'Allow express invoice to synchronize with Inventoria'
and type in the authentication number you created in Express invoice i.e. 1234. click OK & OK again.
Now go back to Express invoice and 'Retrieve Locations and then 'Update Now'.
I hope this helps you out