I have completed the certification program, but after 24h I do not have the badge yet? Can you assist?
Is is correct word formation and can I express my thoughts in better more natural American language?
It might be an improvement to phrase your sentence slightly differently:
I have completed the certification program but not yet received the certificate that I expected within 24 hours. May I ask you kindly to follow this up?
The expression can you assist is perfectly correct. My phraseology is just a little more polite.
The phrase but after 24 hours can easily be understood in context to mean 24 hours after completion of the program but it's not idiomatic in this sentence.
The word badge would indicate either an object made of cloth or metal that would be attached to a garment or similar.
If the acknowledgement you expect is a document, the word certificate is appropriate.
If you merely expected confirmation, then say so.
If you actually expect a badge, change my suggested wording accordingly.