Unable to send OTA updates to SIM

The setup: - I am using Osmo-MSC, Osmo-HLR, python-smpplib, and sim-tools. My SIM card is a Sysmocom USIM-SJS1 which came with OTA keys. - Osmo-MSC has been configured to accept SMPP connections, and dcs-transparent has been set. - Using sim-tools with the --smpp flag, I generated the necessary SMPP messages to load the HelloSTK.cap file to the SIM. (Essentially, I've followed the instructions here: https://osmocom.org/projects/cellular-infrastructure/wiki/Shadysimpy) - Sim-tools outputs 6 messages, so in a separate program I use python-smpplib to push each message to the MSC over SMPP. - The send function in my program looks like this: parts = ["027000003815060115150000001dbf31df8eb85248617ff79260f7bf0abd332e2b3c> "02700000901506011515000000d85420f0f778e35b4b8e0ae5d961593444f20fdebb> "02700000901506011515000000729062e3cc920acc51be4f22fd067314bfaee313d6> "02700000901506011515000000373f30a3c12b494d3089c70a2dd46e33e3fccac790> "0270000068150601151500000083f04c39ef2df571bd5389f71b8c528e9b3edea046> "02700000601506011515000000ad6eeebc9373de8bd3a8888324ffaad4d8cd935f0c> ] for part in parts: pdu = client.send_message( source_addr_ton=smpplib.consts.SMPP_TON_INTL, source_addr='0', dest_addr_ton=smpplib.consts.SMPP_TON_INTL, destination_addr='3331112222', short_message=bytes.fromhex(part), data_coding=246, esm_class=64, registered_delivery=True, ) print(pdu.sequence) I have Wireshark running on the computer hosting the MSC, and it shows GSM SMS messages sending to the UE, however there is no response, and when I inspect the SIM card, no applet has been loaded. Am I missing something here? What could be causing this issue? Thanks!