Given so little detail it appears the new gear is simply defective. You will encounter folk that this because it's now, it can't be faulty.
when I connect an old router and establish a connection, and then immediately afterwards connect the current router, everything appears to work fine. but on rebooting the current router the connection is again "destroyed" :-
ADSL internet connection (wired to PC in bedroom & wireless) slowed to almost zero (10 Kbps! - the connection got slower & slower through time).
contacted ISP who suggested connecting to the test socket (in the hall).
decided first of all to connect an old router to the master (but not test) socket (in the hall) together with different cabling & splitter/microfilter - everything starting working almost perfectly (apart from downstream data rate was considerably lower than expected each time I connected - between about 1400 & 1600 Kbps - I have max. 8 Mbps).
when I connected back my current router everything continued to be OK (apart from low downstream data rate) - until I would restart the current router and everything went back to very very slow!
I then decided to replace current router with old router in the bedroom itself, so this time using the same telephone socket, cables etc. as for the current router.
Again everything started working well, but this time the downstream data rate is 6496 Kbps! I swapped back the current router, and everything is at this moment going fine.
BUT I just know that if I restart my current router it will be back to very very slow again!
does anybody know what's going on?!
(p.s. I had a problem a few months ago where the internet would go down for a time, sometimes for hours, but the ISP had no idea what was going on. I think it could have been a NAS drive connected to the router that was causing the issue - is this possible? It would seem that disabling the NAS drive would fix the problem - it is still currently switched off)