This would be an odd situation.
It is also not clear from the circumstances whether Panama law would or would not apply to the case. Other possible jurisdictions that could apply would be the jurisdiction of organization of L, the domicile of C, the jurisdiction that is home to the financial institution where the PIC invests its funds, the jurisdictions where the powers of attorney, respectively were executed, the jurisdiction of the lawyer drafting these instruments, or the jurisdiction named in a choice of law clause in the relevant documents (which might not be uniform). As a practical matter, the law of the jurisdiction which provides a forum to resolve a dispute resolving the matter in question usually ends up applying, unless there are no facts that support that choice of law or there is a consistent contractual choice of law that calls for the law of another jurisdiction to apply.
An entity can always act through its officers or managers, and usually, entities do not grant blanket powers of attorney to individuals as a result, instead, they usually appoint a natural person as an officer or director or manager of the company. An officer, director, or manager (or even employee for that matter) of L could clearly utilize the Power of Attorney naming entity L as an agent-in-fact of entity C (even if they were appointed after the Power of Attorney from C to L was executed).
And, the provision barring "substitution" is probably not relevant because L would be the person acting under the power of attorney from C whether it was acting under the authority of a director or a manager or an officer or even someone with a power of attorney from L to act as L's attorney-in-fact.
This said, usually the power of attorney naming P as attorney-in-fact for L, would not expressly including a power to act on behalf of L in situations where L is acting as a fiduciary for a third-party, and the default rule would usually be that a power of attorney that does not expressly grant such a power does not include such a power.
Some jurisdictions would even flatly prohibit someone acting as an attorney-in-fact under a power of attorney to carry out the responsibilities of the principal in the fiduciary capacity (e.g. as an executor, guardian, conservator, custodian, trustee, or attorney-in-fact under a power of attorney).
Also, to the extent that the law is ambiguous, the courts would generally look to the intent of the parties, which is not revealed in this thin set of facts.
I don't have the resources available to me to determine what the law of Panama says with respect to this issue, and it also isn't clear from these thin facts, whether the law of Panama applies, so the difficult search isn't really justified.