There are a few issues with Mendeley properly citing theses in American Chemical Society (ACS) format. Based on the ACS guidelines here, the format for citing theses in the bibliography should be as follows:

Author. Title of Thesis. Level of Thesis, Degree-Granting University, Location of University, Date of Completion.

An example found in the linked PDF can also be found below here:

Unfortunately, the way Mendeley provides the output, the citation format in the bibliography is as follows:

Author. Title of Thesis, Level of Thesis, Degree-Granting University, Location of University, Date of Completion.

Note the period after "title of thesis" in the original, but not in Mendeley's format.

Technically, the information for "level of thesis" is only provided by the "university" and does not make use of the "type" section at all, nor is there a section for the location of the university (see below), and so what I have done is incorporate the type of thesis and location of university all in the "university" section for Mendeley Desktop. (This issue is secondary to the other issue I brought up.)

It seems that this issue is at least somewhat exclusive to Mendeley, as based on the same CSL, there's no issue in the format (see below). However, a minor note is that there is a colon after University of Cambridge and Cambridge (not sure if that's important).

I'm quite unfamiliar with coding so if someone could help fix this, I would really appreciate it!