If a GIMP brush works inside a small rectangle but stops at its edge, an old selection may still restrict the operation. Hiding a selection outline changes the display, not necessarily the selection itself. Test that state before replacing the brush or reinstalling the application. A floating selection is a separate condition and is not removed by Select None.
Describe the boundary of the failure
Work on a copy and identify where the brush succeeds and fails. A repeated sharp boundary matching an earlier crop or selection is useful evidence. A brush that fails everywhere suggests other possibilities, including the active layer, locks or tool settings. Do not assume that every ineffective stroke has the same cause.
Check whether selection display has been hidden. An invisible outline can leave the user with no obvious reminder of a still-active region. If the task requires that region, preserve it before changing the document. If it was only a temporary selection from a completed operation, removing it may be appropriate.
Change only the selection state
This is a reproducible test plan, not a measured result. On a duplicate, use the same brush and the same active image layer to make two tiny marks, one inside and one outside the suspected boundary. Undo those marks. Use Select None, then repeat the two marks without changing brush size, opacity or layer.
If both locations now respond, the comparison supports a residual-selection diagnosis. If the restriction remains, do not keep issuing the same command. Check layer extent, the active mask, locks and the tool. Record which single change actually affected the result; changing everything at once makes it impossible to identify the cause.
Do not confuse a floating layer with an ordinary selection
GIMP's Select None cancels ordinary selections but does not affect floating selections. Look in the layer stack if pasting an item also prevented editing other layers. A floating item may need to become a new layer or be anchored to the correct target, depending on your intent.
For a portrait retouch, a leftover rectangular selection can protect the cheek but prevent a brush from touching the collar. That is different from a floating logo pasted above the portrait. The first situation concerns operation scope; the second concerns a temporary layer state. Use the evidence in the layer stack to choose the appropriate action.
Rebuild intentional scope before continuing
Removing an accidental selection does not mean that every later edit should be global. Recreate the smallest appropriate region for the next correction, checking the whole subject and its surroundings. Keep destructive brush work limited and preserve an untouched layer for recovery.
Acceptance means the brush responds in the intended region, remains restricted only where you deliberately chose a boundary, and introduces no new marks outside the approved task. Undo diagnostic strokes, save an editable master and inspect the final export. This is an external GIMP workflow; it does not establish a matching selection command in Imagild. Use Imagild's available editing controls according to the current interface rather than carrying over assumptions from another application.