What should I do if my DTV visa application was cancelled due to nationality errors?

This is not the first and last time. It happened to my friend who submitted his application from Vietnam. They cancelled not even mentioning what was the issue and he literally walked to the embassy to ask and they told him he filled his nationality as Vietnam but there is not a chance in any way that actually happen when he filled it. It seems that either the system is somehow malfunctioning or the Thais are using this way to generate more yield from applications

Are they using VFS to process the applications, if so then try another location ?

Two different things: For place of passport issued, should put your country, not the country where the embassy is located. However, it is not clear if that is the issue here, since they specifically referenced UAE and not Dublin Ireland. I believe, but could be wrong, that there might be two locations where you enter your nationality, once when you create your account on the e-visa website and then in the actual DTV application. If so, it is possible that the screenshot here is pulling from your account information while you mistakenly wrote UAE on the application.

Have you renewed your passport in Dubai by any chance and when they ask place if issue of your passport you entered UAE by nay chance?

Country / territory of passport is not the same as nationality.

You chose the right nationality but wrong country of passport.

Did you supply one or other of these required documents to allow you to apply via that consulate?

Valid UAE Residence Visa (for those working, studying, or as a family member of a UAE citizen) or

Valid UAE’s Resident Identity card (Emirates ID)

Can you book an appointment to go in? Print out everything and see if they can rerun it