getting UnAuthenticated Connection error when executing custom functions from employee account

getting UnAuthenticated Connection error when executing custom functions from employee account

Greetings

i'm testing a custom connection between zoho books and expenses, i created the connection from zoho books side and enabled the "use logged in user credentials" option. the custom function uses invokeUrl to add entries to zoho expense. when i tried it from my (org admin) account it worked successfully. but when i tried running it from a test employee account i got - UnAuthenticated Connection "connection name" - error. why is that happening? how can set the connection up as accessible by employees and not admin only?

Thanks