Sending a message with a maximum of 160 characters works well, as it will send everything in a single SMS. As soon as we reach 161 characters, and the message has to be sent in 2 SMSs, we never receive the message. The delivery logs indicate that the message was sent out successfully, even though we never received it, and the message doesn't even appear in the ClickSend logs.
The treshhold is set to max 8 messages at once, so the issue isn't there. I'm also not aware of any limitation of the sorts in the external account.
I contacted Support, who says it's an issue at the provider's side, as the logs indicate the message was sent. I also contacted ClickSend, who says the issue is at Adobe's side, as they don't have any trace of those messages arriving and being bounced or failed.
I am stuck in loop between Adobe's and ClickSend's support, so the experience of the people here seems to be my last resort.
Can anyone please help or share ideas ?
EDIT : We found the solution! Multi-part messages only work when the option 'Enable message payload' is checked in the external account. Even Adobe's support wasn't aware of this, we found it out ourselves. The downside to this, is that the 'billable message count' for those multi-part messages will always be 1 instead of the real value.