There may be a problem with some mod/plugin on the server (read the server’s log for more info), or your player’s data may have been corrupted somehow.
To note, this isn’t Hostinger support, just the forum for AMP, but we can lend a hand with panel-related questions.
You can look at recent log messages in the Console tab, or you can find the logs/latest.log file inside the File Manager tab after managing the Minecraft instance.
As to deal with corrupted player data (if that even is the problem), you can save a copy of your player’s data world/playerdata/yourplayersuuid.dat (uuid can be found in the log, or here https://mcuuid.net/).
Then once you have a copy of that data you can try and use some online tool to restore it, or download a tool to edit it.
Though the easiest way is to restore the player data from a backup if you have one.