DDWRT Router as Repeater not connecting since upgrading to Plusnet Fibre

[#1]

Hi
Apologies if this has been posted before 
I have an old Linksys router WT45G that i have previously used with DDWRT (v24r2) as a repeater with an old TG585 router before i upgraded to fibre. Since upgrading and now using the Technicolour TG 542N this does not work. The fibre router does not even recognise the repeater router in the access devices.
Is there something setup on the TG542N router that is blocking a repeater as ddwrt appears to be configured correctly.
Many Thanks

[#2]

Were you perhaps using WEP security with your previous wifi setup?

[#3]

No i was using WPA

[#4]

Is the TG582n and Repeater using the same fixed wifi channel number (ie. 1, 6 or 11.  Do not use AUTO) ?
Perhaps also try manually setting the TG582n to use specific wireless security modes.  eg. WPA1-PSK(TKIP)  or better WPA2-PSK(AES).
Does DD-WRT need updating on the repeater?
From within DD-WRT, can you do a 'site survey' to see if it lists the Plusnet wifi network?