If you are in a hurry, you can also ask by phone, which is the most direct and can best express your attitude. However, it should be noted that when making a phone call, the language must be concise, to the point, and not too wordy.
E-mail inquiry is also a more formal way of inquiry, if you want to ask by email. You can reply directly in the email that HR invites for an interview, or you can identify yourself in the email inquiry. When to interview, what position, and if you like this position very much, you can also express your recognition of the company.
The job search went well.
First of all, if you can't read it back, it may be that the other party is busy at hand and happened to meet your message and forgot to reply. If the situation is not very urgent, you can wait patiently first. After all, the most important thing in job hunting is to have a patient heart. The second situation may be that you are really not interested in finding a job and have excluded you from your thinking.
In this case, you can usually try to ask questions, such as sending a message to the other party saying that you still have a useful internship experience and so on. Test each other and see if they are still interested in you. In short, I can't understand most cases, but the company has lost interest in you, and many times I have to start looking for a new job.