3E4424237952324825077A09503005702970D754206CF3FFA5A2EE90103E42049140ACA625243A7DC4550DB811208D8299D7A34EB9ECBEE9CD751A685F0FF05D1A3D004F320600211B
This is the packet I received from a wm-bus (OMS) water meter, it's striped of CRC bytes.
As I get it from the OMS documentation this is the CBC initial vector:
24237952324825070909090909090909
And AES password is: 1111111111111111
As I get it the first AES block that needs decoding is:
702970d754206cf3ffa5a2ee90103e42
And after decoding the first two bytes should be 2f 2f but they aren't.
If you do not get 0x2F 0x2F then the short answer is: you took the wrong aes key.
Detail:
You seem to take the right bytes and derived the right IV for this OMS telegram. If the first 2 bytes of the decrypted part do not result in 0x2F 0x2F then this indicates that you have the wrong AES key for this telegram.
You say your key is 1111111111111111 - but what is this? An AES-CBC Key for OMS works with 16 bytes (128bit). You only have 16 characters, but to express 16 bytes in hex you will require 32 characters. So there is something fishy with this key:
0x01010101010101010101010101010101 is not working.
Neither is 0x31313131313131313131313131313131 (which is 16 times 1 in ASCII)
However I was successful to decrypt with
0x11111111111111111111111111111111
//Decrypted telegram:
3E 44 24 23 79 52 32 48 25 07 7A 09 50 30 05 2F 2F 0C 13 00 02 00 00 02 5A F5 00 02 FD 17 00 10 02 FD 74 ED 16 C2 01 6C DF 17 CC 01 13 00 02 00 00 2F 2F 2F 2F 2F 2F 2F 2F 2F 2F 2F 2F 2F 2F
So in the end it looks like you just took one half of the key and that's why the decryption failed.