Make each part independently dependable
Choose one short phrase rather than the entire song. Play its chords with a simple rhythm until you can maintain the pulse without watching every finger. Separately, speak the words or use neutral syllables in the vocal rhythm while tapping the beat. You need to know where the phrase begins, where it crosses a chord change, and where it ends. If either layer is uncertain alone, combining them often produces a tangle that feels like a general coordination problem rather than a specific missing skill.
Combine speech with reduced accompaniment
Mute the strings and keep a small strumming motion while speaking the phrase. Next, add one chord attack at each harmonic change, leaving out the full pattern. Continue counting internally through any vocal pickup. The word that starts a line may not coincide with the new chord, so check the recording rather than moving your hand whenever a new sentence begins. Use the synced lyrics in AudioChords as a location aid if helpful, while keeping the audible pulse as the timing reference.
Restore melody and rhythm gradually
Sing the phrase over the sparse accompaniment, then add one element of the intended strum. If the vocal changes the guitar rhythm, return to the previous version and isolate the exact beat where they separate. Practice the phrase with a measure of lead in and a measure after it so that it belongs to a continuous flow. Avoid measuring progress only by speed. Being able to sing clearly while the guitar stays simple is already a functional arrangement. Add complexity when it supports the song and no longer takes attention away from the vocal delivery.