I have been through college athletic recruiting with 2 sons. First because you are posting in these forums you would be looking at D1 and D3 recruiting. There are very different rules that apply. In addition, D1 recruiting has been forced into Quiet Times by the NCAA in response to Covid-19. I would assume the D1 academies have even stricter requirements in terms on on-campus recruiting. All that is context for why you may be getting no response.
Generally - if you are being recruited it is very obvious. If they really want you you will be getting active, personal communications. If they are interested, they will check in and ask for film. If you are "on the board" but not in the top two categories, you wil likely receive consistent email contact.
If that is not happening, then the basics are: send a well written, BLUF email with size and measurables and a link to a short video. Coaches see hundreds of videos - save them pain by getting to the meat quickly, and limit the fancy soundtrack or graphics. If no response, continue to politely follow up with additional video that shows progress. If you are on a club team, reach into the network your coaches may have for a personal connection.
If you are a baseball player, tweet video and tag @flatgroundapp and the program. He will re-tweet and you may be able to access teh coaching staff that way. There may be similar online accounts for other sports, but I am unfamiliar. Hope that helps