For this particular customer, we have the PRTG Remote Probe server and Microsoft Exchange 2010 servers running on Windows 2008 R2. When I added the Exchange Database (PowerShell) sensor to my Exchange server (device) in PRTG, I received an error message on the "Is valid" and "Mounted" channels:
"(configured lookup prtg.standardlookups.yesno_0based.stateyesok is empty or not available)"
I checked if the lookup "prtg.standardlookup.yesno_0basede.stateyesok" exists on the PRTG Core server. You can check this in the "Lookups" folder under the installation directory of PRTG (e.g. C:\Program Files\PRTG Network Monitor\Lookups). In this folder, I only found the lookup "prtg.standardlookups.yesno.stateyesok", so it seems to be a small issue on this sensor type.
Luckily, it's really easy to fix. Edit the channel options for the "Is Valid" and "Mounted" channels. You'll see that the value lookup is listed as "None".
Select the "prtg.standardlookups.yesno.stateyesok" lookup and click Apply.
After applying, the channels of the sensor look like this.
You can use the multi edit option in PRTG to do this for multiple sensors at once. Apparently, Paessler support is already aware of this issue. You'll encounter this issue if you add this sensor while running version 15.3.18 through 15.4.20. According to the release notes, this issue is fixed in version 15.4.21.5161 / 5162. I guess I have to update!
Exchange Database (PowerShell) sensor uses the correct lookup file automatically if you add this sensor anew.