I’m seeing a persistent cellular connectivity issue with a Raspberry Pi using
a Sixfab 4G LTE HAT and a Telit LE910C4-NF.
Current behavior:
LTE registration succeeds
the modem attaches successfully
the cellular interface gets an IP address
ICMP ping works over the cellular interface
UDP DNS works at least to 8.8.8.8:53
but TCP/HTTP/HTTPS over cellular times out
What we already tested:
account is active and not over limit in Sixfab Connect
modem-side data session works
modem-side ping works
switched from ECM mode to QMI mode
re-enabled ModemManager / NetworkManager
QMI bearer comes up successfully and gets an IP
tested multiple public endpoints over the cellular interface
forced registration attempts on both T-Mobile (310260) and AT&T (310410)
Packet capture result:
outbound TCP SYN packets leave on the cellular interface
no SYN-ACK packets return
So at this point it does not look like an application bug on the Pi, and it no
longer looks like only an ECM-mode problem.
Has anyone seen this with a Sixfab SIM / Telit LE910C4-NF before?
Did you resolve it with a SIM/network session reset, carrier/profile change,
or something else on the Sixfab side?
I’m also opening a direct support case with Sixfab, but I wanted to ask here
in case anyone has seen the same pattern.
To investigate this further, could you please provide the ICCID number(s) of the affected SIM card(s) to message option? This will allow us to check the SIM status, network configuration and any potential restrictions from our side.
Once we have the ICCID, we will review the setup and assist you accordingly.
Hello Imran and mgwalkerjr95. I am seeing the same issue exact problem. It’s been two weeks trying to figure this out and it’s incredibly frustrating. Here is my ICCID: ‘8988********665499’ My goal is to push sensors’ data up google firebase. Thank you for your help.
Upon reviewing your account and the associated data usage, we identified the likely cause of the issue.
Your asset is currently assigned to the “Default Networks - 100 MB Limit (Monthly)”Network Group and the data usage for the current billing period has exceeded the monthly allowance (112.09 MB used out of 100 MB ). Once the data limit is reached, device functionality and connectivity may be impacted.
To restore full access and avoid similar issues in the future, you can either:
Wait until the next billing period begins or
Upgrade the asset to a Network Group with a higher monthly data allowance.
If your goal is to continuously send sensor data to Google Firebase, we would recommend selecting a Network Group with a higher data allowance to accommodate your expected usage.
Does the data usage reset on the first of the month? if that’s the case, then shouldn’t the account already have reset since I already put in some amount on June 3 so that I can use the network. Is that not allowed?
Our montly billing is set to 21st of every month. Is that when it will reset?
Please clarify and I appreciate you taking time to explain everything to me in detail.
The data usage does not reset on the 1st day of each calendar month. It resets based on your asset’s current billing period.
In your case, the current billing period is:
22 May 2026 01:26:03 GMT – 22 June 2026 01:26:03 GMT
So the usage limit will reset at the start of the next billing period, not on June 1st.
Adding balance to your account on June 3 does not reset the monthly usage counter. The balance is used for billing/payment but the Network Group limit is a separate monthly usage cap.
Also, please note that Network Group was previously called Fleet . It is a setting used to help protect your account from unexpected or unnecessary data usage. It is not the same as your Data Pool or PAYG balance.
Your current Network Group limit appears to be 100 MB/month and the asset has already used more than that limit. If you need more data before the next reset, you can log in to your Sixfab Connect account, open the affected asset and increase the Network Group limit from 100 MB to 1 GB or a higher option.