The original error message you got explains the problem:
The local and remote VPN endpoints must exist within the same 255.255.255.252 subnet. This is a limitation of --dev tun when used with the TAP-WIN32 driver. Try 'openvpn --show-valid-subnets' option for more info.
Since the address you're pushing (must be coming from your ccd file, although you ddin't post that) is not within a /30 subnet, you cannot use it with Windows clients using the net30 topology, which is the default.
The reason this works on non-Windows is because even in net30 topology the addressing is configured as a traditional Point-to-Point (PtP) interface; Windows has no notion of this concept, and the TAP driver fakes it by using an entire /30 and only using the center-two usable IPs on the fake "subnet."
You have a couple choices, the easiest of which is to switch to using the "subnet" topology by adding:
topology subnet
to your server config, which will also push this topology to clients. This requires that you push addresses with an IP and subnet, not a PtP pairing of IPs, which looks like this:
ifconfig-push <address> <subnet>
The other option is to change the address pair you push to Windows clients to be within a /30, for which you can see all available pairs as indicated in the error message with:
openvpn --show-valid-subnets
Additionally, when using any form of static address assignment, you should explicitly limit your `ifconfig-pool` to
exclude the range you are using for such static assignment. If you don't, it's possible the normal "lowest free address" assignment by the server for connecting clients will pass out the same IP you attempt to set statically for a given client, and this causes issues. Use of ipp can make this harder to figure out as well since it's not "truly static" but just a "recommendation" to the server to use the last IP the client had, if it's available.
Thus I'd recommend that you look at the manpage and expand your `server` configuration option and reduce the size of your `ifconfig-pool` to a range excluding addresses you wish to statically push.
