Issue with Rtools (?) and packages lme and matrix

Newbie on R here. I have to do some geostatistical plot on R, and for that I need the lme4 and Matrix packages. When I run my code, I get the error message

function 'cholmod_factor_ldetA' not provided by package 'Matrix'

From some googling the issue seems to be that I need to install a binary version of Matrix. However, when I try, I get the warning

WARNING: Rtools is required to build R packages but is not currently installed. Please download and install the appropriate version of Rtools before proceeding:

Except, I already have Rtools installed (4.3, my version of R is 4.3.2 and RStudio 2023.12.0). From other answers online it seems to be a path issue but I don't know how to solve it. Also I'm working on a company laptop and I don't have the privileges to install and uninstall software.

Any help is appreciated!