retro_jet

I made this thread after I asked one university immigration official. After that, I asked two more. The first officer said, as stated in the original post, that I should be fine if I have a new I-20 and the SEVIS fee paid. The second said that I should technically be allowed in but there have been cases in which students have not been allowed an entry. And, the third officer said that the SEVIS number on the Visa and the I-20 should match, and therefore, asked me against coming with the same Visa.

As I said in my first reply to your post, your F-1 is still valid if you left the US within 60 days of the program end date on your original I-20 for your master's program, 20 August 2019.  Since you left the US before that date, you have not violated the terms of your F-1 visa so it is still valid.  I would suggest that you take evidence of your July 2019 exit date when you re-enter the US in case they ask you about it.  Also the original I-20 from 2017.  It will ultimately be up to the CBP officer at POE to decide whether or not to let you in, but if you have the F-1, new I-20, and SEVIS record for your new PhD program, and they don't have any concerns upon questioning you at POE, you have a pretty good chance of entering with no problems.  Take any documents to show that you have sufficient financial means to pay for a four-year PhD program in the US including housing and living expenses, and that you intend to return to your home country after completing your PhD because the CBP officer may ask you about that.  Since you can't get a new F-1 visa right now anyway, that's not an option, so try using the one you have, which is good for two more years as long as you're following all policies and procedures which it appears that you are with a new I-20 and SEVIS record.  Good luck!

from what the link is saying and what others have said earlier, it seems like the answer is yes.

College dean in the US here with some relevant experience with F-1s and I-20s.  If you left the US within 60 days of the master's program end date listed on the I-20, the underlying F-1 student visa continues to be valid until it expires, in your case to 2022.  If you left within 60 days of completing the master's program, you did not violate the terms of your F-1 visa, so it continues to be good.  You will need a new I-20 and be entered into SEVIS for the planned PhD program in order to successfully use the still valid F-1 visa to enter the US.  Since PhD programs take longer than 2 years, you will need to apply for an F-1 visa renewal well before your current one expires.  The international student office of your chosen school can assist with this process, deadlines, etc.  Most major universities have experienced staff who are very helpful with processing foreign student paperwork.  You have received good information from the school you contacted about pursuing a PhD.  The problem you face if you want to start a PhD program this Fall is all of the travel bans going on right now because of the virus.  Good luck with your PhD program!