if you can not see delete button on the project which you are sure to have privillege, in most cases this project is created from a proposal.
The error you shown seems these project have invalid reference, check the reference on the project page and also check with it in backend db from following querys(replace project ID/user id for you own). make sure the references are existed.
select * FROM KNTA_REFERENCES_V WHERE STORED_SOURCE_ENTITY_ID = 6 AND SOURCE_ID = <project ID> AND SHOW_TARGET_TYPE_FLAG = 'Y' AND ENABLED_FLAG = 'Y' AND TARGET_TYPE_CODE != '20'
select * FROM KNTA_SECURED_REQ_REFS_V WHERE STORED_SOURCE_ENTITY_ID = 6 AND SOURCE_ID = <project ID> AND SHOW_TARGET_TYPE_FLAG = 'Y' AND ENABLED_FLAG = 'Y' AND USER_ID = <user id who do delete>
Try with these steps if the project stem from proposals
This should not be viewed as a workaround to delete projects on a regular basis.
1) Navigate to the Project that is to be deleted 2) Click on the References tab, note down the Proposal Request #, let's call this "ProposalRequestNo" 3) Click on Search > Requests. In Request Type field, enter the Proposal Request Type (PFM - Proposal or others) used. 4) Select "Include Closed?" to 'Yes', click on Search 5) On the Results page select the Proposal as got in Step 2 6) Click on 'Delete' 7) Using SQL*Plus or any DB tool log on to the schema that the PPM server is using 8) Run the following SQL:
update pfm_lifecycle_parent_entity set proposal_req_id = NULL where proposal_req_id =
9) Go to the project that is to be deleted and click on 'Delete'. The project should now be deleted. 10) Repeat Steps 1 thru 9 for other projects.