[403] Cannot add task to project due to task sharing permission settings of the target project or one of the task's existing projects.

[John_Baldo]

Hi, Looking into this but for the time being I want to point out that projects recently got a setting to restrict who can add tasks to a project and this can impact the “source” or “target” project. This error was introduced to indicate that.

We mentioned this in this post, but I’m realizing now that it was not included in the title and could be missed. Will work on clarifying that.

[ Upcoming ] Custom field permissions value editing: Add new restrictions on custom fields

Summary We’re adding permissions on custom fields values and multihoming in projects. Project Admins will be able to set restrictions on these fields. As a result, certain users may not be able to edit a custom field value or add/remove tasks from or to that project. [Custom field permissions] For example, when restricting editing custom field “Priority” on a project to be “Only Admins can edit that value”, Project Editors will no longer be able to edit the “Priority” field on tasks: [Custo…

Still, I would not expect this to impact your integrations until someone explicitly changed this setting, but I could be missing a behavior change. Can you verify that you are an Editor in both the source and target projects? (note, the API / integration permissions will be that of the person who originally set up the integration unless)