Which is the router currently locked to (MTN, Dialog, etc.)? Are you trying to unlock it for any SIM, or just fix a bug ? Do you have the IMEI or current software version handy?
Updating your firmware can improve connection stability, unlock network bands (openlining), or fix security bugs. Since this device is often rebranded by carriers like MTN, finding the right version is key. Quick Look: ZLT S20 Firmware Manufacturer: Tozed Kangwei . Chipset: ZX297520V3E. zlt s20 firmware