If the current firmware is below 1.208, then a two-stage upgrade process must be done. Upgrade the panel to version 1.208, then upgrade to version 1.243 (current as of this document).
Version 1.209 and above use an encrypted firmware version and file system. Version 1.208 allows uploading of the newer encrypted firmware. Prior versions will fail.
Various firmware versions can be downloaded from the below links:
Version 1.208 https://file.ac/rYAEjz6yhaI/
Version 1.241 https://file.ac/7sXAp_6e9HU/
Version 1.243 https://file.ac/8XNDG7-xVDM/