When the no decision is available, the whole decision category becomes unvisible even if decisions will be available once more later. This is because decisions you cannot take are made not visible instead of not available (greyed out). Due to this implementation, the decision category with the infos about the debt can blink in and out of existence over the months, fooling you into thinking the decisions are not here anymore.
For this specific case, I've found two possible causes
-There's only one nation left to reimburse. The time for the decision to reappear is twice its activation time, so after the decision is over, you have to wait its duration once more for the tab to reappear
-You utilized on of the decisions that allow you to reimburse 50% of a debt at once. These last half the time but no more decision can be taken about the debt for the same duration as a regular decision, so for (I thinkk) 30 days after the decision is over, the tab will not be visible.
This could be corrected quite easily using a mod by making all these decisions unavailable instead of unvisible, and only making them unvisible once all the debts have been reimbursed. Additionally, a visible timer or date telling you when said decision/ when any decision will be available again would be appreciable. Toying a bit with missions and flags, it shouldn't be too hard to implement.
This is one of the few confusing UI decision of this DLC.