You have introduced a fatal error into your feed which is rendering it unreadable in both the Store and iTunes. Conesquently the Store has not updated since, and subscribing in iTunes shows the feed as empty.
A validator (XMLGrid.net) says the error is 'near' line 120, character 373. This image shows you where line 120 is:
I've obviously counted 373 characters along, but it looks as if an unacceptable character is inserted here:
That sign indicates an unacceptable character. Other appearances of it indicate a line or paragraph return, which doesn't seem to be causing any problems (there are a lot of them) but as you see there is no break here. I've no way of detecting what this is - possibly a line as opposed to paragraph break.
These problems tend to arise from copying text into a feed from a word processor. This can bring over formatting characters which are not allowed in XML, or characters such as 'curly quotes': both will wreck the feed. Whatever it is, you need to remove it. In any case, iTunes does not read the 'content:encoded' tag so it is completely redundant there.
There may be other instances (XMLGrid.net will flag only the first one it finds) though any episodes which were previously visible in the Store would presumably be OK.