Seems the general concensus is I would have to install the old Weatherlink PC software and update the interval from there but I've always been fussy about what software I install on my computers and it seems very long in the tooth to me.
Having said that it could be my only option?
Yes, WL for Windows is old software - its development was stopped several years ago, bar occasional bug fixes and the like. Weatherlink.com is where all Davis development effort has focused in recent years. That said, WLfW still works perfectly well and is still the preferred program for some users - its only real issue is the rather dated UI and if you can look past that then it's still good robust software. And if you want to change the archive interval on the logger then yes it's probably the simplest option and runs perfectly well on Win10.
I'm still waiting a reply from Davis but I might give them a call this afternoon due to my station not transmitting data and I'll broach this issue with them as it looks to me that although I have a Pro subscription I am still only seeing the standard interface with no device & alarm options through Weatherlink.com.
Looks like I need to repeat this:
What you see on weatherlink.com configuration options depends considerably on your upload device. Legacy upload devices like WLIP and USB/WLfW uploads don't support remote device configuration (there's simply no back-channel available to the logger) and alarms are set locally at the logger/software rather than via wl.com. IF the alarm flag is triggered then an email can be configured via Notifications | Email notifications on wl.com for legacy devices. To see the full set of options you need a Weatherlink Live unit.