installed Debian 8.6 and need to reinstall linux 2.7

just installed Debian 8.6 from usb/dvd, all looked good, (only to find I should of not over written linux) now update manager just will not work, tried apt-get update. What should I be looking or reading about? I have a linuxcnc-2.7-wheezy.iso why will this not reload?

Many thanks for any help!
Just don't know what I am looking for.

Many thanks tommylight, for your help! I have try several ways to install a file (linuxcnc-2.7wheezy.iso), I believe this is the most recent stable release of linuxcnc. After reading

(forum.linuxcnc.org/9-installing-linuxcnc...xcnc2-7?limitstart=0)

"grub" the OP has several steps he used, I get stopped at "synaptic" command or "synaptic manger win/tab" will not recognize the USB thumb drive or file. After reading more at

(forum.linuxcnc.org/forum/9-installing-li...ion-on-debian-jessie) it may appear from quote from

"Todd Zuercher"

"Unfortunately that announcement about support for Jessie with RTAI may have been a little premature. (Someone really should add a note to that page with updated info.) Some time not long after that announcement was made it was found that that RTAI kernel version was crashing buildbot, so it was shut down and per-compiled versions of Linuxcnc are no longer available for it. It is unfortunate because I also feel that Jessie is much more polished/better release otherwise than Wheezy."

Is this still the case, or is there a workaround? What I need is a recent OS that works well with a linuxcnc package to run cutter path software on a mill.

Many thanks for all who may help in advance.