The dash (-) in front of the chatId is a MUST for group chats. For a regular chat, there is no dash.
You might want to look to the config of the telegram action. Maybe you tested more config’s and the action didn’t save properly the new one.
Take a look here HowTo: Manage OpenHab 2 configurations, section Some useful Karaf console commands.
Try and view the current telegram config in karaf console:
config:list "(service.pid=org.openhab.telegram)"
If the displayed config doesn’t match the one from telegram.cfg you should delete it and let the action re-load the config from file by restarting openHAB.