If someone has had an abortion and they can't fast for 60 days, will Allah forgive them if they constantly ask for forgiveness?
There are two opinions on that. According to the Palestinian scholar Dr. Hisam al-Din Afana if a person cannot fast in that scenario, there is nothing else they have to do, they can go on with their lives as Muslims (but of course praying for forgiveness is always a good thing).
A second opinion, mentioned by Ibn Qudama al-Maqdisi, is that the person will have to feed sixty people in the place of the sixty days of fasting. A fatwa on the Egyptian scholar Sheikh Yusuf al-Qaradawi’s IslamOnline website recommends this second opinion. (Here is an archived PDF link to the Arabic article on IslamOnline that mentions these opinions)
The second opinion seems more likely to achieve the intent of the law, which is to make the person feel the gravity of their sin and, just as importantly, to give them a sense of closure, so that once they have finished making their offering they can go on with their lives instead of continuing to feel guilt and uncertainty. Some Muslim charities like IslamicRelief offer a “kafara service” where you donate money specifically for the purpose of the expiation of sins and they will find sixty people to feed on your behalf.
If a person cannot afford that, they should wait and have the intention of doing it if and when they can.