I hope you are all doing well.
I've been using Deluge for around 4 months now and I must say as a client, Deluge is superb. It's simple, effective and really easy to interpret especially as a new comer to such field.
I am new to these sort of clients and applications and it has been working flawlessly ever since I installed it.
This being said, yesterday and this morning I have noticed a little error poke in the bottom right corner of the Deluge Client with the text 'Port Issue' as can be shown here:

Upon inspection, it reads that the client is unable to establish any incoming connections. When clicking the icon my 'Preferences' tab is opened shown here:

When attempting to test active port on both random and manual, they both return the Warning triangle symbol, the client seems to pull peer's but is unable to form a connection to them shown here:

I assume there seems to be an issue with port-forwarding, but I am not entirely sure what could have caused this as no major changes were made to the client apart from a dark-ui interface mod, which was performed a month prior. Could this be an issue with the router?
As mentioned before, I am still new to this scene and do not have extensive knowledge on these subjects but I will do my best to understand.
Operating system: Microsoft Windows 10 Pro
Version 10.0.19045 Build 19045
System type: x64-based PC
Deluge version: 2.1.1
Client: 2.1.1
libtorrent: 1.2.15.0