I keep getting cellular test radio has timed out
Your firmware shows as 4.2.0, that is likely the issue. Firmware version 4.4.1 added a critical software fix for a possible cellular connection bug which can cause the panel to not connect to cell network again after dropping connection.
Your panel started responding to Alarm.com via broadband, so initial signaling is going through, but to fix cellular communication updating firmware is needed.
Firmware updates are incremental on the IQ Panel 4. You would need to update to 4.3.0, then to 4.4.1 using the patch tags and instructions in the guide linked below.
After updating firmware to at least 4.4.1, does that resolve your cellular connection?