I've downloaded nearly every adobe app available in the google play store and I'm still unable to open some adobe forms on my mobile devices. The same message always pops up: "Please wait... If this message is not eventually replaced with the proper contents of the document, your PDF viewer may not be able to display this type of document. You can upgrade to the latest version......." The message goes on to give links which are supposed to redirect you to the upgraded version, however, I already have this downloaded. Why am I unable to view certain adobe forms on my mobile devices?
I assume by Adobe forms you really mean PDF forms. There is no such thing as Adobe forms.
That having been said, there are two types of PDF forms, the original AcroForms and something known as XFA forms. Either one or the other may be in a PDF file although XFA forms are in the process of being deprecated from the PDF specification and should not be used unless you can guarantee that the form will be access and filled with Windows or MacOS Adobe Reader or Adobe Acrobat.
XFA forms are not (and will not) be supported in either iOS or Android versions of Adobe Acrobat Mobile Reader. This may be the issue you are encountering. (FWIW, XFA forms are not supported by most PDF reader software from third parties!)