I had issue with the same rim and tyre, almost felt like giving up .. but then it worked after I put some sealant in and rolled the tyre so the beads are coated. Then the obvious stuff like no bubbles on tape, smallest possible valve hole etc.
There are definitely some issues with dt rims and tubeless tyres. Amey's solution should work but I use fairy liquid or other detergents and if the tyre fails to go up I remove the tyre clean the tape with ipa, and fit more tape then try again. This way there is less mess.
Tried seating the tyre with an inner tube. Didn't help.
Thinking of investing in air blasting gadget. cO2 or one of those air blaster pumps; which is best?