smart tv = limited cache/memory and no possibility to use vpn.
mag box is old fashion... better get an android box and you will enjoy best flexibility, you can install all apps and also vpn.
e.g. amazon fire tv stick OR xiaomi mi box.
No typo in server url, username, password?
Sometimes username or password include small L or capital (big) i letter, have special attention to O and 0 (zero). Try also to reduce bouquet list, in some cases the device has limited cache/memory.
most smart tv's having limited cache/memory, and some ISP put speed limits (throttling) on iptv servers... DNS change and a VPN would be helpful in this case, best would be to get an android box where you can install apk files and vpn etc.
Instead of "http://myiptv.server.com/get.php?username=USERNAME&password=PASSWORD&output=ts&type=enigma22_script"
you can use "http://myiptv.server.com/get.php?username=USERNAME&password=PASSWORD&type=m3u_plus&output=ts" = that's your m3u link/file ;)