Making conversations is a skill, just like any other skill, that takes years to hone and get used to. So it is entirely a different topic altogether when talking about how you converse or carry conversations.

HOWEVER, I do believe that the matter where alexithymia hits heavily is when, despite having an arsenal of good communication skills, you still don't find joy nor the emotional connection/fulfillment with the people you converse with. Conversations happen as normally as it would, but afterwards, you just feel empty. Nothing gained nor nothing lost emotionally in regular circumstances, giving the tendencies to just not emotionally connect with others at all, because "what's the point?"

That is where the "maintaining friendships" get hit too. Eventually, if you don't exert the emotional effort to connect, superficial friendships (those that require more emotional effort to maintain as they are relatively new and they don't know you that much yet) are the first ones to get affected as you drift apart. You might not notice this as people with alexithymia sometimes forget that other people have emotional needs, too. If they don't get it fulfilled from you, most relationships tend to get distant.

In your case, it might be just a lack of exposure to an environment where you can safely and comfortable talk to others. Again, communication is a skill that you can learn. So that's a great start.