If wxtide isn't running at all, and you are not getting a populated list of tide stations, then there are a couple of possibilities:
1. Check the install directory for wxtide, and in particular the name of the harmonics (TCD) file. Make sure there isn't a '~' in the filename, which happened sometimes when - for some reason - wxtide adhered to the old Windows 8.3 filename convention and the longer name of the harmonics file was abbreviated. If you do a "manual" install of wxtide (just download the zip, extract to a directory of your choice), this doesn't happen.
2. ReefMaster uses a temporary file when generating the tidestation list and also when extracting tide times. The process is that RM runs wxtide and has the output sent to a temp file. This file is then read and parsed for the necessary information, before being deleted. RM uses a Windows function to get your TEMP directory, but this is not guaranteed to exist or be writeable (although it is almost always both). Ensure that your TEMP path exists and is writeable. To find the TEMP path that Windows is using, open up a command prompt (Windows Run/cmd) and type "set"/Enter. You'll see a list of environment variables, including TEMP and TMP. Windows will use TMP first or, if that is not set, TEMP. Have a look at these environment variables and make sure that the directory they point to exists, and that you have permission to write to it.
Note: if your temp paths are not set up correctly you are also going to have a bad time exporting to AT5, as temporary files are required during this process also.