Debugging the AX Debugger can be a little bugger'. Here are a few things to check for as to why you aren't able to debug some code.
Make sure your user is added to the Debugger group on the instance your in
IMPORTANT: You'll want to log out and back into your instance. This means actually logging out and not just close and reopen AX and/or the RDP session.
This might be the issue if the debugger pops up but is greyed out and AX seems to have acknowledged the breakpoint but breezed right past it
Make sure your breakpoints are set and enabled and not 'disabled'.
There is a button next to the set breakpoints in the toolbar that allow enable/disable
Assure the code where your breakpoint is is actually being hit.
This is a make sure its plugged in type response but you'd be surprised how common it is...
In your user options under Development tab, make sure the 'Debug mode' is set to 'When Breakpoint'
The breakpoint might be set in a spot that the debugger can't hit. For example, the clicked method on a button.
adding a line of code for 'breakpoint;' rather than using the red dot breakpoints will allow you to debug these methods
If the code is running in the CIL, you may need to make the code run on the client.
Go to your user options > 'Development' tab and uncheck 'Execute business operations in CIL'.
If the code is running in batch, you'll need to debug this process via Visual Studio. The breakpoints in AX are for client processes only generally.
You may need to adjust the breakpoint check boxes in the Dynamics AX Configuration Utility under the Developer tab. There are two settings there: 'Enable user breakpoints to debug code in the business connector' and 'Enable global breakpoints to debug code running in the Business Connector or client'
Check the AOS debugger settings. Dont remember what this check box(es) are called but there is something on the AX AOS config that can be a factor.