Thanks for reaching out to us, I am sorry this is not working as expected.
Thank you for the testing details and system models! Unfortunately 4K 60Hz support only reached the Mac Mini in 2018, all previous models are limited to 30Hz refresh rate, likewise the 2013 MacBook Pro 13" is only capable of 4K 30Hz, the Early-2015 MacBook Pro 13" added 4K 60Hz support ( from Apple’s documentation here: https://support.apple.com/en-us/HT206587 ). In either case the miniDisplayPort to DisplayPort cable will provide for the maximum possible resolution on this monitor with these computers, and can provide for 4K 60Hz with supported systems.
I am sorry this adapter is not working at 30Hz, this may indicate a faulty adapter or an incorrectly negotiated connection with the display ( possibly caused by the 10-bit per color channel settings in this monitor ). Since this adapter will not be capable of providing a better connection than the miniDisplayPort to DisplayPort cable I would be happy to expedite a return and refund for this adapter. Please let me know your Amazon Order ID ( available from Amazon.com/orders ) for the original purchase of the adapter and I can approve the return right away. If you would prefer to send the order ID via private email, rather than this public forum please email me at ‘firstname.lastname@example.org’ with the subject line ‘Ticket #268217 - Attention Pat’ and include the Amazon Order ID in the body of the email and I will reply back with a prepaid printable return shipping label and return instructions.
I am sorry for the inconvenience.