Have you selected the device type as "Cisco DX80" while adding this device in CUCM. Can you try adding it as "Cisco TelePresence DX80" and see if that helps.
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If you are running CE software and getting the "error: sip registration failed: 485 Ambiguous/ Device type mismatch" you must have added it as Cisco DX80. Cisco DX80 is used when it is on android software. You will have to add it as Cisco TelePresence DX80, see below Check "Migrate a Cisco UCM registered DX device to CE software (page 1 of 5)"
If you are not seeing that option then you will have to upload latest device pack to enable the same. You can download the device pack from link below.
Make sure you installed it on PUB first and then all SUB and perform a cluster reboot to the device pack to take affect.
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Just got a brand new DX80 with CE8.3.1. I added it as a DX80 at first and had the same problems. Deleted and added back as a Cisco Telepresence DX80 and it worked fine. I have CUCM 11.5.1SU3a.