having trouble uploading photos

I think Silverstripe v2.4 / PHP 5.3

Someone else set this website up for me a while ago and now the ‘Browse’ button to upload photos in CMS doesn’t work so I cant add new photos. I was told I have to do a full upgrade, but trying to avoid this.

Any ideas?

Well, the short answer is… find out what’s changed.
I’m guessing maybe something in the hosting set up has changed (maybe the PHP version or similar).

The advice you’ve been given is spot-on though. Silverstripe 2.4 was end of life many years ago, and PHP 5.3 was EOL back in 2014. You should really consider updating the site to use current versions of PHP and Silverstripe… there will be many potential security vulnerabilities in the set up you have.