You are trying to process a membership signup transaction within the NetCommunity plugin however you get an error "Unable to update constituent for the following reason: Required field missing: Constituent Code"
We are currently investigating this issue.
In the meantime, the workaround is to manually add the constituent code when processing the Membership signup transaction.
Steps to Duplicate
Please check the following:
1. Edit the Membership part and check under "Additional Fields" that "Allow gifts of Membership" is ticked. 2. Check that a constituent code has been assigned. 3. Confirm that this error occurs when someone who is signing up has made an additional donation.