I have been using Amazon SNS to send SMS for a while, but two days ago it stopped working. I didn't change anything on my side. Even if I try to send SMS from the console, it still doesn't work.
I only have 35% delivery rate for last couple of days, but since yesterday it is not working at all.
There are different ways to troubleshoot this problem. This is something addressed in the Developer Forum of AWS. Please go through the following steps to troubleshoot this problem. These could be basic steps, but I am pointing out the most general steps required.
Where required by local laws and regulations (such as the US and Canada), SMS recipients can opt out, which means that they choose to stop receiving SMS messages from your AWS account.
For Account spend limit, type the maximum amount in USD that you want to spend on SMS messages each calendar month. When Amazon SNS determines that sending an SMS message would incur a cost that exceeds your spend limit for that month, Amazon SNS stops publishing SMS messages within minutes.