Few weeks after Ultherapy, more sag in neck and jawline! (Photo)

It looks like you were more a candidate for neck lifting or platysmaplasty however, if you have sagging ultherapy alone will not get it to completely tighten you would need a combination of things.  Options include for skin tightening:
thermage radiofrequency
ultherapy high intensity ultrasound
PDO nova threads for lifting
btl exilis ultra, venus legacy, and thermi250 for constant collagen stimulation
facelift/necklift with fat grafting/fillers
ThermiRF internal heating and tightening please see an expert for a formal evaluation. Best, Dr. Emer.

Its hard to see much of a difference from the two pictures you have posted. Suffice to say at the very least, just wait the full 4-6m- and compare to the preprocedure pictures, rather than the ones taken right after- it will give you a more objective view of the results.

I find Ultherapy very effective for tightening under the chin and neck area as long as there is no fat present. In 4 years of using the Ulthera I have not seen any fat reduction and this is generally a limitation under the chin. I often reduce any fat pockets with a fat busting injection we have Aqualyx or Kybella in the USA.
Just be patient, Ultherapy does take time, because the tightening is a healing response to the ultra sound stimulation and takes 3-6months.