Help with Clematis Montana Rubens please

Hi Shell, and welcome to Gardeners Corner . Sometimes getting Clematis "off the ground" can be frustrating and disappointing as they can be a bit finicky. They will get off to a good start and then start drooping.
One of the things I have discovered is that Clematis do like to be planted deeply, at least 3 inches lower than in the pot level. They do like, as you say. cool and moist roots, and you're watering every day would have helped. It is difficult to diagnose problems with any plants from a "distance" but I would suggest placing a mulch of compost around 2 or 3 inches over the root area and watering it then........then water every other day and then feed with a soluble general feed [like Miracle Grow] once a week.
The clue to the problem might be that the Clematis in the shade is happier and although you think the root area of the unhappy Clematis is cool it may not be as cool as the Clematis might want it initially. Placing a mulch over the root area will help or the alternative is to place a large flat stone over it......but I would recommend the mulch. I could have suggested digging up the Clematis and planting it deeper as another member has done but, to be honest, it risks aggravating the condition of an already unhappy plant by disturbing it. Clematis in shade. depending on the variety, might be less willing to flower as profusely as one in the Sun but you only find that out after you've planted it.

 

Let us all know how you, and the Clematis, get on. I think patience is the word with it