Israel conducted further strikes overnight against Gaza in order to test the tenuous ceasefire:

Israel Defense Forces (IDF) strikes overnight, killing at least two Palestinians and wounding others, have placed new strains on the cease-fire unfolding in Gaza Strip, as reported by The Guardian, Reuters and Investing.com (all three +3 providers).
Though both sides maintain that they remain committed to the U.S.-brokered ceasefire agreement, recent attacks demonstrate its tenuous nature.

Israeli forces initiated the violence when they bombarded a location in Gaza and shot dead an individual, according to Palestinian news agency WAFA. (Sources) Reuters also reports on this incident.
Three people have died due to injuries sustained from earlier strikes. The truce, implemented roughly three weeks ago, was meant to halt major combat operations and set into motion hostage and prisoner exchanges; however, many underlying issues still haven’t been resolved as of yet. Investing.com.
At the core of this dispute lies a question of compliance with truce terms: Hamas was meant to free all living hostages in exchange for approximately 2,000 Palestinian prisoners while Israel agreed to pull back troops, stop major offensives and grant greater humanitarian access. Arab News
However, both parties have accused one another of breaching provisions: Israel claims that Hamas has failed to hand over bodies of dead hostages and allowed militants from Gaza territory to carry out attacks, while Hamas denies this charge and accuses Israel of using this truce as cover to resume attacks – something Hamas denies and blames on Israel using as cover to resume strikes (The Guardian.com).
One of the most serious tests came early last week when Israel responded to the death of one of its soldiers by conducting large-scale bombardments that killed at least 104 people in just 24 hours, according to Gaza health authorities.
Arab News That attack raised serious doubts as to whether the cease-fire could hold, with recent overnight strikes suggesting it only remains so in name. While IDF officials maintain they remain committed to the deal, their words seem far removed from actual action on the ground. Investing.com
Humanitarian aid remains in short supply in Gaza after two years of conflict have destroyed it and resulted in at least 68,000 confirmed deaths according to health authorities in Gaza. Arab News recently provided more details.
Thousands remain displaced, infrastructure is destroyed and aid agencies warn that any return of large-scale fighting will further destabilise the enclave.

Why has the truce fallen apart so rapidly? In part, this may be due to vague language in the agreement regarding key issues — disarming Hamas, withdrawing Israeli forces and reconstruction timelines — being left undiscussed; however, this short-term pause was never meant to end the wider war, but only stop further hostilities from unfolding.
Second, both parties retain strong motivations to press their agendas: Israel insists on security guarantees while Hamas and other militant factions look for relief from blockade, freedom of movement and reconstruction projects. Thirdly, external mediators such as Donald Trump’s administration in the US face limited leverage when it comes to enforcing compliance on the ground.
At risk is a short-term lull in hostilities rather than lasting peace. For it to hold, both sides must rebuild trust, fulfil commitments regarding hostages and prisoners, create meaningful mechanisms of verification and accountability and establish meaningful verification procedures; without this process in place, small escalations events such as overnight strikes will continue testing its tenuous halt and could easily rupture it.

As such, while the truce in Gaza may provide temporary respite from Israeli strikes, recent events have demonstrated its fragility. With unresolved issues remaining and military actions returning again and again, this deal stands at an important juncture; without both Israel and Hamas moving from tactical pauses towards strategic engagement it will only remain as temporary respite rather than becoming the basis of lasting peace.