Being left on read usually feels worse than it is. Most of the time it means the person got busy, not that they are done talking to you. The worst move is a needy double-text like hello?? which signals anxiety and lowers your value.
The fix: wait, then send one light, low-pressure message that gives them an easy reason to reply.
Replying to your own message minutes later reads as anxious. Give it real time. Silence on your end is far more attractive than a string of unanswered texts.
Never ask why they are ignoring you. Send something they would enjoy responding to, like a callback to an earlier joke or a light question.
One sentence. No paragraph about your feelings. The goal is to lower the barrier to a reply, not raise it.
One light follow-up after a day is fine. Avoid multiple unanswered messages, which read as needy and make it harder to re-engage.
A few hours at minimum, often a full day. Waiting signals confidence and gives them space to come back on their own.
Send one more light message a few days later. If there is still nothing, move on. Their silence is your answer.