Updating fields on leads/contacts via API v2 no longer triggers workflows

Updating fields on leads/contacts via API v2 no longer triggers workflows

We recently switched to using API v2 for our integration. We update certain fields on users to be able to trigger workflows, however this no longer works.

The fields are being updated correctly on the contact or lead, but no workflow is triggered. When I manually update the field the workflow triggers correctly.

We need to get this back up and running as soon as possible.

Anyone any advice regarding this issue?