Is it alright to ask recommendation letter from the same professor more than once? Background: I was applying for grad school last year, and asked my professors for a lot of rec letters(likely 15 programs which made the work really tedious). They kindly agreed and send all the rec letter much earlier before the due date, and the outcome is really good, I had been admitted by almost all the excellent universities which I thought I won't had much chance, so I suppose my professors' recommendation helped a lot and I am very grateful.
However, the problem is, due to complicated reasons I had to reapply this year, and I'm not sure whether it would be appropriate to ask professors who already helped me once again since I already troubled them too much last year. And I didn't contact them after I send them a thank you letter which made me feeling like the only thing I did after graduate is keep asking rec letter from professors. I could find enough rec letter from my intern supervisor since I had graduated for a while but my friends told me universities really value the rec letter from undergraduate professors so I better at least have one. My current plan is that I would ask them if they still have the rec letter they wrote for me last year and if so, I will awkwardly ask them again. I really appreciate what my professors already done for me and I really don't want trouble them. It appears to be a very hard time for all universities and professors because of the CVOID situation, so I'm not sure if I should even bother them at this point. Please let me know if my plan would be culturally appropriate or not. I graduated from an american college if it matters.
tl;dr: yes, but do explain the circumstances.
Professors are well aware that writing recommendation letters is part of their job. We know that good letters are a requirement for students to advance, and if students have behaved reasonably well in their interactions with us, we should gladly provide such letters. I had a student apologize to me for asking me to send five letters to distinct employers, so I can understand your reflex to not want to be a burden. Let me reassure you, just as I reassured that student: it is not a burden at all. Writing recommendation letters is a bit of work that results from having had interactions with the student that I enjoyed.
All that being said: you probably will want to make sure that the professors will understand that their work has not been in vain. Thank the professors for their efforts so far, express that you are very happy with the achieved results, and tell them that you unfortunately must ask for a little more of their time. Then write the reasons why you couldn't accept any of the spots last year, and ask them to send the same letters again (only updating the cosmetic stuff, such as the date).
It may be difficult to be open about your personal circumstances to the professors. However, it is probably necessary to tell them why you couldn't make use of the opportunities last round, since this motivates why the professors wouldn't be wasting their time this round. If you write it like that, I would find this request absolutely appropriate, and I would be surprised if your professors wouldn't respond positively.
Good luck with the applications!