Try "wet & forget outdoor" to refresh the brick patio. It's available at Lowe's, walmart.com, & QVC.
Weeds should be killed before you try to fill in the cracks with mortar.
You can try boiling water or this weed killer:
If your email is directed to someone named Betty you need to email her directly. If you put landscape fabric or weed barrier down first that will eliminate most of the weeds. I spray weeds that pop up in between our pavers with a salt vinegar combo. Just use in full sun as that helps dry out and kill the weeds.
Power wash or hose off and use a bit of dawn dish soap and a stiff bristle push broom. Hose off. Let dry. Then use polymeric sand to fill in the cracks.
You will still get random weeds here and there. Weeds are spread by wind, wildlife and people. Dribble boiling water on them or give them a squirt or two of white vinegar.
Here's how we keep the weeds away between our bricks, Betty: https://www.frugalfamilytimes.com/2012/09/how-to-make-weed-free-brick-driveway.html
This is the most effective all-natural weed killer DIY that we use. It's even been featured on Hometalk! Hope this helps! Hugs, Holly
Check your local DIY lawn store. They may have a product to use on your patio that permanently gets rid of weeds until you change the soil. That's what we did with ours.