Hmmm - so HTTP fails (“not allowed”), but TCP works.
Could this be another case where your modem doesn’t have the necessary “Commercial Features” enabled?
See: https://forum.sierrawireless.com/t/smtp-internet-protocol-feature-not-activated/3845/9
And: https://forum.sierrawireless.com/t/faq-forum-wiki/3491/15
You should talk to your Distributor about this!