Forerunner 245 frozen - after restart it stays on the triangle

Dear,

I woke up this morning and my Forerunner 245 was frozen and giving me the time as 00:00. After holding down on the light button for the restart, I then clocked on the light again but it stays on the triangle.. totally unresponsive since.. Tried the restart again but same issue. 

Thanks in advance for your help.

Kr,

Benjamin