Not accustomed to the land or water
To feel as though one cannot adapt to changes in one's environment
Neutral
她一到外地就水土不服，看来很不适于出差 | Tā yī dào wàidì jiù shuǐtǔbùfú, kàn lái hěn bùshì yú chūchāi
She has a hard time adjusting when she goes to foreign places, so it looks like she's not suited to business trips
[Source]
外国人到中国旅游，可能会水土不服，最好带些常备药 | Wàiguórén dào zhōngguó lǚyóu, kěnéng huì shuǐtǔbùfú, zuì hǎo dài xiē chángbèi yào
People taking trips to China may have a hard time acclimatizing, so they should bring along some common medicines
[Source]
None
水土不伏 (shuǐ tǔ bù fú)
This is generally used when you're not yet adjusted to a new environment. A great time to use this is when you go to a different country and experience major culture shock.
《三国志》(Sān Guó Zhì) by 陈寿 (Chén Shòu). The historical text covers the events of the end of the Eastern Hàn Dynasty (东汉, Dōng Hàn, 25 - 220) and the Three Kingdoms period (220 - 280)
This chengyu is from a line in the work listed in the "Origin" section above