In most cases, delays in the delivery of messages are not associated with any problems on the channel, since in case of overloads and delays in the delivery of several messages in a row for at least one minute, we have a monitoring signal and the channel of this operator is turned off.
Any mobile phone can sometimes lose the network for a short time or be unavailable for receiving messages, for example, when a re-registration took place in the operator’s network, there was a bad connection, data transmission via the Internet, loss of signal, call or transmission of another SMS message, as well as when the subscriber was in roaming due to the peculiarities of work of foreign operators. In such cases, a new message is delayed in the SMS center of the operator and repeated after a certain period of time, which may cause delays in delivery. Subscribers do not always notice such problems with their phones, as this is a common situation in GSM networks and they can claim that their phone was available when there was a delay in delivery.
A long-term delay in the delivery of messages or the inability to deliver can be caused by a disconnected phone, an overflowing message buffer, or a damaged SIM subscriber's card. You can check the availability of such a number by calling, but in some cases, when the phone is turned off, the call may take place due to the configured call forwarding, which does not work for SMS messages. If you find such problems, you can try to delete old SMS messages and restart the phone, move the SIM card to another device, remove forwarding, or specify the final number to receive messages.
In any case, there is no cause for concern, we monitor the quality of our channels. But you can send us any suspicious numbers for analysis.