▲张老师说得对，最常见的用法可能是 have problems (in)doing sth。但如果不从常用性来考虑，以下表达都是对的：

have problem (in) doing sth（problem 为不可数名词，相当于 difficulty）

have little problem (in) doing sth（problem 为不可数名词，相当于difficulty）

have no problem (in) doing sth（problem 可视为可数或不可数名词）

have a problem (in) doing sth（problem 为可数名词）

have problems (in) doing sth（problem 为可数名词）

▲查了一下手头的词典以及平时收集的资料，罗列以下例句供参考：

We have little problem (in) finding where they are. 我们要找到他们在哪里没多大困难。（陆谷孙《英汉大词典》）

They seem to have problem getting all the furniture upstairs. 他们把所有的家具都搬到楼上去似乎有困难。（葛传椝《简明英语惯用法》）

My grandparents have never had a problem accepting me. 我的祖父母从来都是无条件地接受我。（《柯林斯Cobuild高阶英汉双解学习词典》）

Even though our house is in tip-top condition, we're having problemsselling it. 虽然我们的房子状况很好，但现在把它卖出去还是有困难。（《剑桥高级英语词典》）

On past records, she should have no problem passing the exam. 从过去的成绩来看，她通过考试应该不成问题。（《牛津英语搭配词典》）