The cache is not at the published coordinates which are for a convenient car park near to where the cache is hidden.
You need to open the following webpage which is password protected. The password can be deduced from information on this cache page. Solving the password is the only puzzle in the whole series of 11 caches.
Click here to enter password
The webpage will tell you the coordinates for the cache box. There will also be instructions in how to find the information which will enable you to find rest of the caches in this series. (full details not there yet, but coming shortly) The walk to find the rest of the info starts a couple of miles away, and is often muddy, so appropriate footwear is needed. Collecting all the info will take 2-3 hours. Armed with all the letters, you can move on to the next 10 caches. The walk to collect the remaining 10 caches in the series should take another 4 hours approximately.
Sadly, a few of the caches in this series have been archived during my retirement from geocaching, but the are still plenty to find.
For this whole series, please replace all the caches exactly as you found them and don't leave any spoilers in the logs. I hope you have as much fun finding the caches as I did in setting them.