Weeping Pine Tree Turning Brown
Hello and thank you for asking about your tree. This appears to be a Weeping Blue Atlas Cedar (Cedrus atlantica 'Glauca Pendula') with Cedar Needle Blight, also called tip-blight. This is a fungal disease, and spreads during this time of year from last year's infected needles. Cultural control is to remove and destroy (don't put in your compost nearby) the diseased plant parts and debris caught in the branches and under the tree.
I'm a volunteer and unable to make a site-visit, so this is my experienced best-guess as to the problem. If this is a valuable tree in your landscape, consider hiring a certified arborist who can come see it and possibly offer solutions I am unable to.