If you see an asterisk * instead of a number, often with an error code if using Point Info (tag browser), then communications is bad to the device or the tag has a invalid address.
1. If all tags on a com port show asterisks, then the communication port or device is possibly disabled in the Station Status Display.
2. If the device and comport are enabled, and all tags show asterisks, then communications to the device are lost (i.e. able unplugged) or the device is off-line (powered down).
3. If only one or a few tags in a device show asterisks, then the address for the tag is probably invalid.
You should contact an engineer or technician and describe the tag name.