Why I'm not getting an offer, even I did well in the many rounds of interview?

Myself working as software developer and having nearly 6 years of experience. Now am looking for job change and attend many interviews here what I get response from the companies.

Interviews are scheduled by their HR (confirms that my profile is matching for the job position over the call) and not just a walk-in.

Initial Round:

• They ask me to do online assessment test / small programming task.
• They confirmed me that I score 95~99%, so my profile short listed to next level of rounds.

Technical (F2F) Round 1

• In this round, questions are simple to me so I answered almost everything.
• Recruiter confirms that I'm satisfied him and will proceed to next step.

Technical (F2F) Round 2

• In this round, recruiter gave an exercise to do by programming or writing logical concepts.
• I given the satisfied and more relevant answers to the questions. Most of them were correct.
• Finally, recruiter asked my current CTC and expected CTC. After that let me to wait for final round.

After sometime the HR person approaches me and said that I'm not performed well or i've very long notice period (30days) so this is the reason we will not proceeding your profile further.

From my point of view:

• Even I passed all the technical rounds why they just ignore my profile without proceeding to the final round.
• Also, I want to know: What can be the reasons to decline my profile.

For your information

• I'm not a over confident
• I don't show wrong attitude