Can’t transfer ownership to client

I’m working on a customer’s website and I activated the Glossary plugin.
His name is Eric his email [email protected]
Problem is when I logged in the glossary was in my name and email address.
I transferred ownership to him (several times).
I got a confirmation that the process had completed normally

At the other end he gets the following code

I think we have a serious problem here.

Can you please help me set up the account in the name of my client (with his secret KEY) and HIS email address properly?

{“path”:”:\/installs\/install_id\/users\/user_id\/ownership-change.json”,”error”:{“type”:”AccessForbidden”,”message”:”Install [6006879] not authorized to access User [4042283].”,”code”:”unauthorized_user_access”,”http”:403,”timestamp”:”Thu, 19 Nov 2020 11:15:07 +0000″},”request”:{“authorization”:”FSLA 6006879:z_viFjgP62nxvo4fBGNODrAfcjJCT2sGpoqF7-x_nLgMdX4IvoxYXad40xlKtXezc9tq3EXKJp_riBK_mhoGdjIFL0MpWZquwslKkeuaMp0IjNnRj8n5T5A1-y3e6YeqSWUVzKado_DLnQ2ZimOzgVedtkfiPjS2-sRHcvVPv36iROemmQ9Opuxsoxavr8D1c3xE3DR3xZNPgUakYmZK4OVy0i4fEpivXUZ1CLXkCO3pvIT7gqgcG7H9YS_nkzy43QWgoIIrRl_4LlaqpNu_Z02PVmws6M4unPCpUanYuD0″,”token_salt”:”5c4da52fc00fb351755602fe3ede4541″,”owner_token”:”df24bb62edde7bd4b06561966cf36c86″,”email”:”[email protected]”,”after_confirm_url”:”https:\/\/www.selceon.com\/newwww\/wp-admin\/edit.php?post_type=glossary&fs_action=change_owner&page=glossary-account”,”install_id”:”6006879″,”user_id”:”4042283″}}

The page I need help with: [log in to see the link]