Issue ping from router A to Router C

Hello Geeks,
I am preparing for CCNA reading Lammle's book
I follow instruction on the book but cannot ping from Router A to Router C. See my Diagram .
If am doing process with ipv4 is ok .

IPv6 is giving me problem.
Here is configuration.
Router B has two subnets
int f0/0 is configured ipv6 address 2001:db8:3c4d:1::1/64
int f0/1 is configured ipv6 address 2001:db8:3c4d:2::1/64

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Name: show ipv6int B.JPG
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Router A:i configured :
Ipv6 address autoconfig

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Name: Router A.JPG
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Router C used
ipv6 address autoconfig

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Name: Router C.JPG
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This IPV6 I tried to ping from router A
A#ping 2001:dB8:3C4D:2:201:42FF:FE27:5C02 Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:dB8:3C4D:2:201:42FF:FE27:5C02, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

This ipv6 tried to ping from Router C
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:dB8:3C4D:1:2D0:BAFF:FEC7:2E01, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
now ping int f0/1 of Router B is fine
c#ping 2001:dB8:3C4D:2::1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:dB8:3C4D:2::1, timeout is 2 seconds:
!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 0/0/1 ms