ADHDers and refusal to communicate

Sorry for my English, I am French speaker with an intermediate level in english.

Last March I dated a man with ADHD. Everything was fine for 3 months before he moved for his medical internship in July 2019. No news for 3 weeks then he returned at the end of July to finally disappear for good and started to isolate himself. During our last call phone he said to me: "there is nothing to do, we have to wait for it to pass" and he was happy for the texts I sent to him during these time.

Since then, He has not answered my calls or sms (no message for Christmas, Valentine's Day ..) but continues to read them and we are already practically 8 months later. He doesn’t like texts so we used to call.

And he continues to make his living as if I'm not there. Didn't block me but just don't answer my messages / calls. I know he reads my messages because once he changed his profile picture several times because of a remark I made.

I am sure and certain that he has one / more comorbidities in addition to being HP (IQ more than 140) because I even suspected him to be autism during our first date before he told me he had ADHD. For me he is more ADD. He doesn't like confrontation and doesn't like disappointed people. 

He has no close friends and spend his week-end/free time to read/study medical when it is not his turn to take care of his kid or spend time with family.

During this whole period, I learned about ADHD and it allowed me to be more understandable towards him and to soften my messages little by little. 5 days ago I discovered 3 videos explained was “common” to be “ghost” because Adhders become bored because little by little, you lose interest because relationship is no longer stimulating that at the beginning. Some return, others do not so I do not know what to do with him. Since I discovered this, I sent him an message and look like he took it in the good way because he started to be more connected and he is reading my texts as soon as I sent them. But doesn't anwer. The only think he hid was changed his picture profile on WhatAps and put the one I like. 

I begin to lose patience knowing that we are not soon 1 year later and there is not evolution in our situation. I do not want take this as an excuse because it’s also in his responsibility to find a way for communicate and I told him 

Has this situation ever happened to you ?

I woud like have opinion from 

ADHDers and people in relationship with an ADHDers.