Texmaker and TeXstudio ⇒ Texmaker 4.5 won't show changes in PDF (Mac OS)

[filler]

Hi guys.
I'm quite new in Latex and not familiar with too much coding or other technical stuff, so I need you to answer me as you would answer a six year old

I'm writing a project with a group of other students in Latex. We share the files in Dropbox, dunno if that might affect it. I can open their Latex file and view the pdf in texmaker but it won't show my changes in the PDF when I try to compile it, instead it just shows the same old PDF as before I edited. The others think it's because I'm running it on a Mac, but it has worked for me a year ago, when I worked on a similar project with a group, and had no issues...

Any ideas?

[Johannes_B]

Do you have TeX installed?
If you have, do you get warning or eror messages?
Can you compile a very simple document?
Can you save the tex file, put it in the box and another student can compile it?
Why are other students not looking into this, as they can meet you in person?

[filler]

Yup, I have MaxTex installed.

Yes I do get a few warnings and badboxes which I have attached a screen shot of.

I have tried compiling a very simple document now and it does not want to give me an output. It returns an error box with the following message:

"Could not start the command."/usr/texbin/pdflatex" -synctex=1 -interaction=nonstopmode %.tex"

I looked up the error on Google and it seems other users had the same issue when updating IOS. I'm using Sierra now, used to be running LaTex a year ago without issues, don't remember which IOS I ran back then...
It seems the paths in the preferences are wrong, but I'm not sure how to fix it. I've attached a screen shot of my preferences.

Yeah I can save the Tex file and the other students can open it and compile it with my changes in the output...

Basically my co-students are anti-Apple and don't want to get near it

[Johannes_B]

Please read the announcements for MacTeX with Sierra.

You should get your warnings fixed as soon as possible. People tend to ignore warnings and stuff blows up a day before the deadline.

[filler]

Yup. Did that, couldn't fix it.
I now tried TexStudio instead and it works perfectly, so I'll just use that instead.
Thanks for the help though!