Is recurrent miscarriage, despite adherence to worship and good deeds, evidence of unaccepted acts, and what should be done for prayers to be answered?

Continue performing good deeds and supplicating sincerely for a child, and do not despair, for circumstances change. Do not allow whispers (waswas) to reach you, for blessings are not always a sign of Allah's love, nor is their withholding a sign of His displeasure, as Allah Almighty said: ﴿As for man, when his Lord tries him and honors him and bestows favors upon him, he says: "My Lord has honored me." But when He tries him and restricts his means of subsistence for him, he says: "My Lord has humiliated me." Nay! ...﴾ [Al-Fajr: 15-16]. Your inability to conceive might be for a benefit that Allah Almighty knows, as He said: ﴿...it may be that you dislike a thing and Allah brings through it much good.﴾ [An-Nisa: 19], and ﴿...and it may be that you dislike a thing which is good for you, and that you like a thing which is bad for you. Allah knows but you do not know.﴾ [Al-Baqarah: 216]. So be patient and do not rush.