Since it works on the Cable and not the block, I would suspect the block.....However you already replace that....

So, her is what we know: In building "B" there is a feed cable coming in.
If you put a Jack on that cable directly, the phone works. (That shows that you are aware of the unique (Polarity and 2nd pair) termination that the phones require).
Once that cable is terminated onto a 66m50 block you are unable to get the phone to come up.

Can you please confirm this next part for us?

On a 66 Block there is 4 pins across (labled A,B,C, and D below)

A B C D
1 -> -> <- <-
2 -> -> <- <-
3 -> -> <- <-
4 -> -> <- <-

Assuming Feed cable is terminated down Column A and that the signl is present at column A. Put a butt set on pins A1, A2 and you should here a high pitch tone to confirm this.You should also have the same tone on pins B1 and B2.
Your cross connect should be coming off of pins B1 and B2. If you have sigle on A1 and A2 and nothing on B1 B2 I would suspect faulty pins on the blocks - The "V" of the pin not contacting the wire properly, but putting the Butt set on the pin allows the "V" to press into the wire giving a false positive. Depending on the condition of the tool used to punch the wires
down, can cause this. Sometimes rocking the tool horizontally while on th epin can close up th e"V" and allow better contact.
You did raise two things that makes me question the initial termination. These may or may not have any bearing on your problem though.
1) you pulled the Blue pair off of the 66 block...this isn't easily doe if it was terminated in the typical way - not sure if there is a correct tension guidline out there - since the wires are fairly tight. Terminating it back down would be even harder.
2) you reterminated the whole setup on a new block. There again, depending how the cable was initally installed, that may have proved somewhat difficult.

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