Hi Sana1177,
welcome to the Apple (user-to-user) Community.
Re: "I did not renew Apple Music for a month, then renewed it,
now I can't find my old songs"
Wondering if your old songs still appear in your purchase history.
If so, you can likely RE-download them:
Previous purchases may be available in the "Library" in the Music app.
or
If needed: How to: Redownload music - Apple Support
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Troubleshoot;e-shooting:
If there's an issue when you re-download apps, films or other content from Apple – Apple Support
Eg: says:
“. Learn how to redownload hidden apps or unhide music, films, TV shows, books and audiobooks."
“If you see items in your purchase history but you can't re-download them,
report a problem.“
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Re: And what’s the problem!
How apps, content, and subscriptions from Apple are billed - Apple Support
says:
"If none of your payment methods can be charged, your account shows a
negative balance. You can't buy more items or update your apps until you
update your payment method."
More support if needed:
Apple Music Support website:
Music - Official Apple Support
All the best :-)