Because of Covid-19, we are only able to clean the rooms when the guests are not in their rooms. Thank you for your understanding.
ご質問ありがとうございます。
"Because of Covid-19, we are only able to clean the rooms"＝「コロナにより、私たちは～ときしか清掃できません」
"when the guests are not in their rooms."＝「お客様が在室されていないときに。」
"Thank you for your understanding."＝「ご理解ありがとうございます。」
ご参考までに。
The cleaning ladies won't clean your room if you're in there because of COVID.
The cleaning ladies won't go in your room while you're there due to COVID restrictions.
この場合、次のように言えると思います。
ーThe cleaning ladies won't clean your room if you're in there because of COVID.
「コロナのため、お客様がお部屋に在室されていると、清掃婦はお部屋の清掃をいたしません」
ーThe cleaning ladies won't go in your room while you're there due to COVID restrictions.
「コロナの制限のため、お客様がお部屋にいらっしゃる時は、清掃婦はお部屋に入室いたしません」
ご参考まで！
アメリカ合衆国 
カナダ 
