Since official manufacturer websites are often non-existent for these generic boxes, you must rely on community repositories: ophub/amlogic-s9xxx-armbian: Supports running ... - GitHub
This is the most common problem. You must locate firmware with your exact Wi-Fi chip. Use a file explorer with root access and check /system/etc/wifi/ – look for fw_bcmdhd.bin or similar. Then search online for S905L2 + [your Wi-Fi chip] firmware . amlogic s905l2 firmware link
Open the box and look for the version number printed on the green circuit board (e.g., V1.1, V2.0). amlogic s905l2 firmware link
Below are the most stable stock firmware files for the S905L2 platform. These are typically .img files used with the Amlogic Burning Tool. amlogic s905l2 firmware link