In reply to UVM_LOVE:
I believe you have a wrong understanding of the virtual sequence. Such a sequence has 3 specific things:
(1) It does not create itself seq_items.
(2) It is used to orchstrate the local sequences.
(3) it is started in the test.
In your code it is unclear what you want to do.
You are starting an ahb sequence on the buck_seqr. But this sequences does not exist.
In your test you are starting my_ahb_base_test_seq_c on a null sequencer. But this seems to be a sequence which is a local sequences and has the intention to generate seq_items.