Lots of "Invalid case style" errors -- .clang-format being ignored?

I’m trying to set up my environment to work with a C codebase with C++ unit tests. I’m getting a bunch of these formatting errors in my editor:

I noticed that formatting with vim.lsp.buf.format() works fine according to our .clang-format file.

Upon further googling I found that these errors might be coming from .clang-tidy, which is also present in the repository. I checked the content and the errors I’m getting should not be happening according to what is set in .clang-tidy.

So my question is: Why is this happening?

My setup uses packer, telescope, treesitter, lsp-zero with mason, mason-lspconfig, nvim-lspconfig, nvim-cmp and cmake-tools.

I’m pretty much using all default settings aside from a few key-bindings that I changed.