Is the Umrah valid if the woman performing Umrah circumambulated the Kaaba without a face veil, then put on the face veil during Sa'i?

Wearing the burqa is prohibited for a woman in ihram during circumambulation (tawaf) and brisk walking (sa'i) until she exits ihram, due to the Prophet's (peace be upon him) saying: "A woman in ihram should not wear a niqab nor gloves." The burqa is similar in meaning to the niqab.

If a woman needs to cover her face due to men passing by, she should lower her garment from above her head over her face. It was narrated from Aisha (may Allah be pleased with her) that she said: "Riders used to pass by us while we were in ihram with the Messenger of Allah (peace be upon him). When they drew near, one of us would lower her jilbab from her head over her face, and when they had passed, we would uncover it."

If wearing the burqa was due to ignorance or forgetfulness, there is nothing upon the woman. However, if it was done knowingly and intentionally, her 'umrah is valid, but she is required to offer a fidyah (expiation), which is fasting for three days, or feeding six poor persons, or sacrificing a sheep to be distributed among the poor of Mecca and the Haram.