CNTR low is replay protection doing its job: the counter in your command was not higher than the counter the card holds. Typical origins include a database restore, a parallel sending entity using its own counter, replaying an old campaign export, or a previous command the card accepted and counted while your server recorded it as failed. If more than one sending entity shares a key version they share one counter and must be serialised — that is a design fault, not a transient error.
Usual cause
The counter in your command packet was not higher than the counter the card holds, so replay protection rejected it. Your server is behind the card. Typical origins: a database restore, a parallel sending entity using its own counter, a campaign replayed from an old export, or a previous command that the card accepted and counted while your server recorded it as failed.
What to do
Recover by moving the counter up — it can only increase — then retry. MoreOTA ships add 1 and send again; you can add your own step per network or SIM code in the retry CSV. Repeating the same counter fails identically. Read the card-side value where the card allows it. If more than one sending entity shares a key version they share one counter and must be serialised; that is a design fault, not a transient error.
TS 102 225 §5.1.4