I did not get any invitation now a days. But before that, I got only 3 invitation in 8 month, I joined Upwork about 8 months ago and received 3 invitation only in 8 months.
I don't know what happened.
Please can anyone tell me the exact reason?
Are you saying that over a period of 8 months you received only 3 job invites? And you're wondering why you are not getting more?
First of all, no one can tell you the exact reason you are not getting invited. That would require us to be mind readers of every client who ever passed by your profile and chose not to invite you to their job post.
If you aren't getting invited it's likely due to your profile. I quickly skimmed it, and it could use some work. You need to set yourself apart as unique from every other freelancer who does what you do. Your opening lines are pretty boring and not written well. You list your English proficiency as Fluent, but your question here and your profile do not show the writing skills of someone who is fluent in English. I would change that to conversational. When you claim skills you don't have and it's obvious to the client, it brings into question the credibility of every job skill you claim to have.
Remember the first two lines in the profile are most important, and yours are not good. Starting with "Hi" is irrelevant. It's not a letter, it's a profile page. Starting with your education is pointless because your education is already listed on your profile. That text box is there for you to say what's not listed in other places. Make your case for why you are unique, the best, the fastest, whatever sets you apart.
Hope this helps and the invites begin to flow. Otherwise, you have to do like the rest of us and apply outright to jobs and spend a few connects.