After installing Paratext or updating to a newer version of Paratext, sometimes the Paratext.exe file or other files vital to Paratext are missing. This might happen immediately after installing/updating or several days later.
Sometimes this is caused when an anti-virus program removes an important Paratext file. Ask a support person to check the history or quarantine of your anti-virus program and restore any missing Paratext files. Then turn off the anti-virus program while you complete the installation or update. Afterward turn the anti-virus program back on.