The reason the map is empty is because the mesonet-map-json.php script is getting a 500-Server Error instead of returning data.
no data..no map.
Looking at
https://www.txweather.org/mesonet-map-check-versions.php shows that you are missing:
mesonet-map-lang-en.txt
and all the other mesonet-map-lang-*.txt files .. put them back on your site and it will likely work again.
Those files contain constant definitions that are used throughout the script set.. at a minimum, the -en file has to be there to work.