This might help some others.
If you have the Products module ENABLED but do not use it, and instead use the Xero inventory, you will find today that it no longer fetches autocomplete data when typing your products into the invoice creation form.
If you want to use the Xero inventory to populate your invoices via Pipedrive, you must ensure the Pipedrive Products module is DISABLED - the two pieces of functionality do not co-exist.
@Manuel Oliveira it would be great if there was a toggle that could be used so that the invoicing part doesn't break - i.e, invoice products from Pipedrive or Invoicing App. I have some clients who use both the Product catalog and Xero Inventory, depending on the customer they're servicing. These clients (perhaps few and far between?) would now need two instances to use Pipedrive.