If you're receiving an error while submitting a lead on behalf of your partner, this is why.
When a partner registers for the first time, the portal owner will need to Approve the organization and accept them into the partner program. You can find any pending partners by visiting your Dashboard and viewing the "Pending" registrations. You will also see these under the Partner tab if you filter by "Pending."
Once you select the pending partner, you will approve the partner by accessing the drop-down on the partner profile. See below:
Once a partner is approved, they will not be an Active partner until they set up their credentials to your portal and log in for the first time. Once these steps take place, they will automatically become an Approved partner.
In order to submit a lead on behalf of your partners, they will need to be an Approved partner. From there, the approved partner will be available in the partner drop-down list. See below: