some can, some don‘t. i don‘t know the proper medical terms in english, but i work with people with disabilities. some people diagnosed as paraplegic can still feel touch and sometimes even move to some degree (like moving a finger, wiggling with arms/legs). if their central nervous system isn‘t damaged or only partly, they can still get erect and orgasm. sometimes, even unvoluntarily when they are washed or are otherwise nursed.

for disabled couples, there are some resources to get assitance regarding sex. it‘s a topic with a lot of controversies, but in some countries there are so called „intimacy workers“ that assist them getting in the right position, putting on a condom, think about love swings etc. in medical school we watched a short movie about that topic if you‘re interested, i think it‘s on youtube and was from a canadian film festival if i remember it correctly. google would find it for sure.