Trying to update a view with ALTER VIEW and it does not happen immediately, then there is most likely a contention for the table with another process (user).
To find out what is blocking, start the alter statement again, then execute the following SQL, for SQL server,
look at the Blk By column (blocked by) against the row that represents your login and check that the “Command” column has the ALTER command in it. There should be a number of the SPID that is blocking the ALTER command shown where the dashes are shown above.
Use that ID to kill the process (if appropriate!). Although the screen shot shows no blockers, if it had 206 as the blocker, then issuing “kill 206” would allow the ALTER to run.
Note you should understand what you are killing and apologise to the user, don’t kill a process that is going to cause data integrity issues later!