Hey, 3.1.12 is about 1 1/2 years old and will have many problems with the latest Joomla. Not just 3.8.8 but a number of updates prior.
I'm no longer a part of DTH with the recent acquisition. I can still assist if you'd like help with updating your DT Register or any other work on your Joomla site. You can PM me if you're interested.
Nathan is no longer affiliated with DTH since the recent acquisition. You can connect with him and get any type of Joomla website help at
www.JoomlaEmployee.com
.