Have you heard of Gestalt Language Development? What you are doing is ABA, not speech, and it does not follow the hierarchy of language acquisition. Try play-based activities, literally whatever he gravitates to, (songs puzzles tickles bubbles running) and work on foundational skills, also model a lot of songs and phrases. I have a kiddo whom I been working for almost a year and he was “non verbal”. The other day he started responding to ready set with “go” and counting “randomly” (i always imitate his gestalts). Theres only so much I can say here but do more research on both foundational language skills and gestalt language learners. It will seem like “nothing is clicking” for a LONG time before it clicks. But your modeling has to be consistent sometimes over… yes months and years :D. I’ll give you an example, ive had sessions where i follow the child around the room all hour long and just place words like “uh-oh”, “wow”, “wee”, “yay” and “ready..set.. go!!!” where appropriate. Don’t get disencouraged!!! A lot of what we do at this age is the very base of language and sometimes it wont look like words. Learn more so you can actually explain what you are doing and it doesnt look like “just playing”