Hi first time poster and very green at Siemens PLC and HMI.  Only just recently purchased S7-V16 and WinCC.

So we have two S7-400 PLCs and two TP1200 comfort panels that were installed about three years ago when we did a new project.  Everything has been great until recently.  The original programmer added an alarm log for the unit operators to see all the alarms that have been in recently.  

The alarm screen is now blank.  Just displays the normal alarm screen but with no tags.

I do remember during commissioning we had the same problem until he realized we needed a USB flash drive in there and then it worked fine.

When I compare the two comfort screens that are next to each other, the non-working ones USB card is not flashing, the other however that is working is constantly flashing.  

I removed the USB stick and put it in my computer.  There was only one small file on there and the file was called alarm_log_10.csv.  However in the configuration setting under Historical data It says alarm_log_1.

I tried formatting a new USB stick, 8gb, fat32, put it in there.  The USB flashes for about 10 seconds then shuts off and still does not work.  Simulated new alarm.  USB is still blank when removed.

Wondering if I need to cycle power to the screen to get the comfort panel to start working again.

Hope someone has run into this before or can provide advice.  Tried researching this but couldn't find anything.

Thanks.

Figured I'd give an update on this since its been fixed. 

Cycling the power to the screen resolved the issue.