Please note that you wrote to the ResearchGate community, not to the RG team. - It looks like RG has an agreement with that journal to upload metadata and full texts, but I am not sure. Neither of the two authors is a member of RG. What is your relation to the authors, to this paper or to the journal?

Dear Francisco Farnum

According to https://revistas.up.ac.pa/index.php/centros/issue/view/465 the paper you refer to is missing. It is either retracted by the journal or withdrawn by the authors.

As indicated by Wolfgang R. Dick all papers of the corresponding journal are uploaded automatically (and apparently at that particular moment the paper was still present in the volume and issue nr.).

Either the paper will disappear somewhere in the future by 'itself' (which is unlikely since the journal 'simply' removed the paper without any notice) or the journal/authors/you(?) should ask the RG team to remove the paper.

See for more info for example https://help.researchgate.net/hc/en-us/articles/14293099743121-How-to-make-content-private-or-remove-it where at the bottom they state: "We sometimes make a full-text available where a publication has a Creative Commons license. If you feel that a publication has been wrongly attributed a Creative Commons license, please contact us at www.researchgate.net/contact."

Best regards.