Thanks for the update. It is really strange that you are having problems, as I can see all of the (locked) private forums and access to the link to apply with a non-mod standard account (as SP has also mentioned).
There must be something else going on, so hopefully there's enough information for IB / admins to start looking for the cause.
The only other thing might be down to browser add-ins / ad-blockers that might be preventing access - unlikely, but might be worth trying with a different browser / add-ins disabled.