The panel was investigating UNRWA's adherence to the humanitarian principle of neutrality. It is likely that Germany resumed cooperation with UNRWA because the UN agreed to adopt the 50 reforms the panel recommended.
From the Executive Summary of the report:
FINAL REPORT FOR THE UNITED NATIONS SECRETARY-GENERAL
Independent Review of Mechanisms and Procedures to Ensure Adherence by UNRWA to the Humanitarian Principle of Neutrality
The Group was created to assess whether UNRWA is doing everything within its power to ensure neutrality and respond to allegations of serious neutrality breaches when they are made, taking into account the [
] context in which it has to work, especially in Gaza, and to make recommendations for UNRWA to improve and strengthen in this area, if necessary.
This followed allegations made by the Government of Israel in January 2024 that some UNRWA staff may have participated in the 7 October 2023 terror attacks on Israel.
The UN Secretary-General also activated a separate investigation by the UNs Office of Internal Oversight Services (OIOS) to determine the veracity of these allegations, which, if proven true, would be horrifying in addition to being a grave violation of their obligations towards the Organization.
https://www.un.org/sites/un2.un.org/files/2024/04/unrwa_independent_review_on_neutrality.pdf
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The Chair of the panel, Catherine Colonna, is optimistic that the 50 recommended reforms would be implemented and that UNRWA's compliance with and adherence to the humanitarian principle of neutrality would improve.
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Ms Colonna also held a news conference after the release of the report.
Colonna emphasized Monday that Israel cooperated with her team and that it was not within her mandate to examine evidence against individual employees in connection with Oct. 7. That was a separate mission, she told reporters.
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Speaking at a news conference at U.N. headquarters in New York on Monday, Ms. Colonna said she wanted to be very clear that the question of involvement in Oct. 7 is a separate question, one that remains under internal investigation by the United Nations.
https://www.washingtonpost.com/world/2024/04/22/unrwa-israel-hamas-report-palestinians/