Can't connect to/sync using new Server setup

Question

Hi all,
I have set up a new Server and cannot seem to use it to sync, which is its purpose -- requests time out. I also cannot "Connect to server" from the Mac it resides on (suggested troubleshooting step someone gave me). Here's the background:
I'm a brand-new didn't-wannabe server administrator with OK but rather rusty technical knowledge.
I've set up Server in order to provide a local (non-Cloud-based) WebDAV sync server for OmniFocus as Apple in Yosemite (as I understand) removed the ability of 3rd party developers to use the OS's built-in WebDAV server to sync. So Apple stopped supporting the developer, the developer stopped supporting me, and here I am, doing the best I can, but I'm in over my head at the moment.
Here's my system:
MBA, mid-2011 / 4GB / 250 GB
HD with only 6GB free but I've gotten rid of the alert
Mac OS X 10.10.2
OS X Server 4.0.3
OmniFocus for Mac 1.10.6
iOS 6.1.6
OmniFocus for iPhone 1.15.1
I changed defaults for both the long and the short names of the server, edited them in the server overview window (the changed short name didn't take!). In the Settings tab of same, nothing is checked, which I wonder about. In Access, at the moment out of desperation I'm allowing all users and all networks, and still no dice.
In File Sharing, I turned file sharing on, set up my sync folder and shared it (again, out of desperation) with all users and all networks.
In the log, besides a lot of (to my eyes) gobbledygook, I see something like the following lines which seem significant, every time I try to sync from OmniFocus, either on the Mac itself or on my iPhone:
Apr  6 12:44:35 [servername].local OmniFocus[1642]:  SecOSStatusWith error:[-34018] The operation couldn\u2019t be completed. (OSStatus error -34018 - Remote error : The operation couldn\u201a\304\364t be completed. (OSStatus error -34018 - client has neither application-identifier nor keychain-access-groups entitlements))
I can't find any documentation on the error codes.
Omni Group staff advised me to try connecting right from my Mac to the server also on the same Mac through Finder > Go > Connect to Server. If entering the server address (https://[servername].local), it times out in about 10 minutes in the same way OmniFocus does. In the same dialog, if I choose browse instead, I find that within the Server folder are aliases to both [servername] and [servername.local], and they both behave as if they were opening the very top level of my HD.
I'm at a loss for what to try next now, so would appreciate any sage advice.
Thanks!

Answer 1

I'm also wondering, from somewhat similar problems I've read, if permanent IP addresses might make a difference?
At the moment our household router gets its IP via DHCP from our telco provider, and I believe it in turn provides DHCP IPs to the devices on our home network. As this is working fine at the moment and I remember the old "if it ain't broke" adage, I don't intend to try changing this setup unless someone with some experience tells me I ought to. But I thought I'd throw it out there.
All "Connect to Server" and sync attempts are still timing out and this is a work-critical application I need to get running, so any info that could point me in the right direction is appreciated. Even if it's some piece of documentation I need to read. Thanks.