Multi-site Domain Mapping Not Working build plugin page – build plugin page –

I read that using domain mapping with 2 multi-site builds on one IP was not doable. But my server tech told me they could set up an .htaccess rule to make it work.

They setup the rule and now points to but when I try to map it I get the following

result when I try to map domain in –

Not sure what the issue is or if I am beating a dead horse trying to get this to work.