Quick answer: When a game suspends (the console sleeps or the player switches away) and won't resume correctly, crashing, freezing, or breaking on return, it isn't handling the suspend/resume lifecycle. On suspend, the game should pause and preserve state; on resume, it must restore everything, recreate graphics resources, re-establish audio, reconnect networking, and continue cleanly. Handle the platform's suspend and resume events properly; correct suspend/resume is also a console certification requirement.
Consoles (and handhelds) suspend and resume constantly, the player puts the console to sleep, switches to another app, or the system suspends the game, and expects to come back exactly where they were. A game that crashes, freezes, or breaks on resume fails this basic expectation, and because suspend/resume is a certification requirement, getting it wrong can also block your console launch. The fix is handling the lifecycle correctly.
Why Games Break on Resume
Suspend/resume is a lifecycle the game must handle: on suspend, execution is paused and the game should prepare (save state, pause); on resume, the game continues, but the environment may have changed and resources may need restoring. Games break on resume when they don't handle this: graphics resources lost/invalidated during suspend aren't recreated on resume (causing a crash or broken rendering, similar to alt-tab device loss), audio isn't re-established, networking/connections dropped during suspend aren't reconnected, time/state assumptions break (a long suspend means a big time gap the game doesn't handle), and the game assumes it was running continuously when it was actually suspended.
So a won't-resume bug means the game didn't correctly handle being paused and brought back, it's trying to continue as if nothing happened when graphics, audio, connections, or timing actually need attention after the suspend. This is distinct from PC because consoles enforce and frequently exercise this lifecycle.
How to Diagnose It
Reproduce the suspend/resume cycle on the console (suspend the game, resume it) and observe the failure, does it crash, freeze, lose graphics/audio, or fail to reconnect? Capture any crash on resume; the trace points at what's failing (graphics resource use after device loss, audio, networking). Check whether you handle the platform's suspend and resume events at all, and what you do in each. A crash in graphics code on resume points at unrestored graphics resources; a hang points at something not resuming cleanly.
Bugnet captures crashes with traces and context (and supports console builds), so resume crashes surface diagnosably. But suspend/resume is reproducible by performing the cycle on the device, so hands-on testing of suspend and resume is the primary diagnostic, and it's exactly what certification will test, so you want to validate it thoroughly before submitting.
How to Fix It
Handle the suspend and resume events properly. On suspend, save/preserve state and pause cleanly (pause gameplay, audio, and anything that shouldn't run while suspended), and release/prepare resources as the platform requires. On resume, restore everything: recreate any graphics resources that were lost/invalidated (so rendering works, like handling device loss), re-establish audio, reconnect networking and re-sync any session state (for online games, the suspend may have dropped the connection, so reconnect or handle the disconnection gracefully), and handle the time gap (account for however long the game was suspended). Then continue cleanly from the preserved state.
Test the full suspend/resume cycle thoroughly on the actual console (including long suspends and online sessions), since certification will, and a poor experience here fails both players and cert. After fixing, verify the game resumes cleanly, correct rendering, audio, connectivity, and state, every time. Correct suspend/resume handling is both a quality necessity (players expect to return seamlessly) and a certification requirement, so it's essential to get right for a console release.
A game that won't resume isn't handling the console's suspend/resume lifecycle, recreate graphics, re-establish audio, reconnect networking, handle the time gap. It's also a cert requirement, so validate it.