utorrent issues

[#1]

Hello,
I've just joined Plusnet on the Unlimited Fibre package, and am generally happy with it. I've noticed in the past few days that utorrent doesn't appear to be able to download anything at all (it worked for the first couple of weeks on Plusnet just fine).
Looking closer, it appears that the client is unable to connect to any of the trackers or find any peers. It doesn't matter what I'm trying to download - I've tried Linux ISOs galore - the client can never reach the trackers. Very occasionally the client will find some peers via Peer Exchange, but that's pretty rare. I should add that this occurs throughout the day and night - it does not appear to be time related at all.
As soon as I connect to my work VPN, everything springs to life and it all works perfectly. Similarly, as soon as I connect to my neighbour's BT WiFi (with their permission!) everything works fine. But once I disconnect then everything dies.
Looking at the traffic in Wireshark, I can see zero responses to the uTorrent UDP packets.
I wonder if there's some restriction that's been placed on my account?
Thanks!

[#2]

make sure your broadband firewall is set to off https://portal.plus.net/my.html?action=firewall and have you forwarded your ports?

[#3]

Thanks dvorak. Indeed my firewall on that link is off. I haven't setup static port forwards, I've never needed to before (I used exactly the same Buffalo router when I was with BT just a few weeks ago), and as I noted in my original post, as soon as I connect via a different connection it works immediately (without any forwards being setup).
Now this is the weirdest thing...
1) I can visit http://torrent.ubuntu.com:6969
2) If I click on any file on that page, everything just hangs. For example, I can't access http://torrent.ubuntu.com:6969/file?info_hash=%1B_%ADMD%0F%07To%DF%9EQ%9B%1F%25CR%CDF%80. If I look in Wireshark then I see endless TCP retransmissions
3) In fact, if I put "info_hash" in the URL on pretty much any site (even those that have no relation to BitTorrent), then I see the same behaviour - TCP retransmissions and no response.
4) However, a Linux PC on my home network has no issues fetching those files.
I will keep tinkering! Ideas welcome!

[#4]

How embarrassing... it appears it was my wireless access point. It's an OpenWrt based access point, and I suspect it has some built-in DPI for BitTorrent that broke down after being up for a couple of years. Rebooted it and all is well now. Sorry for the noise!

[#5]

glad it's sorted, and a belated welcome to the forum