Fix PLMN Error

PLMN is the core identifier for the mobile network that allows cellular devices like modems to identify and connect to specific carrier networks globally correctly.

What is PLMN?

PLMN stands for "Public Land Mobile Network," which refers to the core mobile network a cellular modem connects to. The PLMN dictates authentication, subscription eligibility, roaming status, APN access point name, and other cellular connectivity parameters for modems and phones.

Many mobile carriers have multiple PLMNs on different bands/technologies (3G, 4G, 5G) that mobile SIM modem routers must scan for and select the appropriate one.


A SIM card used on a mobile modem router must have a valid subscription to register with and be granted access to a mobile network PLMN. Sometimes, the mobile SIM modem router might be unable to connect to the mobile network and get the "PLMN-Not-Allowed" error on the system log, as shown below.

<warn> [modem0] network reject indication received
<warn> [modem0] service domain: cs-ps
<warn> [modem0] radio interface: lte
<warn> [modem0] reject cause: 
<warn> [modem0] mcc: xxx
<warn> [modem0] mnc: xxx 

How to Fix PLMN Error?

The "PLMN not allowed" error usually means an unauthorized or invalid subscription attempt. Some common reasons can also cause PLMN errors. You may follow the steps below to check the potential reasons individually.

  1. Poor Signal Strength: Weak or unstable signal reception can lead to the "PLMN-not-allowed" error. If the signal quality, especially the RSRP and SNR values is too low or floats in a too large range, it may result in this error. You can relocate the route to another spot with a stronger signal or upgrade to higher-gain mobile antennas to fix this problem.

  2. Network Restrictions: The mobile SIM card provider may have specific restrictions that prevent the router from connecting to certain PLMNs. This could be due to roaming restrictions, network access policies, or contractual limitations. In this case, you should contact the SIM card provider to waive the restrictions for your SIM card.

  3. SIM Card Configuration: Issues with the mobile modem protocol, PIN code, and APN settings may lead to the "PLMN-not-allowed" error. You can refer to the mobile protocol settings and mobile APN tutorials to configure them for the router.

  4. Manual PLMN Selection: If the router is set the router to lock the networks or mobile bands that the mobile provider does not support, it may encounter issues if the preferred PLMN is not available or allowed. In this case, reconfigure the router without band locks and reboot it to fix it.

  5. Firmware or Software Issues: Outdated firmware or software on the mobile modem router can sometimes cause connectivity issues. Updating the router's firmware may address these issues.

  6. Network Congestion: In some cases, mobile network congestion or overload can result in the "PLMN-not-allowed" error, especially during peak usage times or in densely populated areas. Please wait a few minutes and try again. You can also upgrade your data plan to priority business or commercial grade to fix it.

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