you can do a continuity test just to be sure which chip is which
but the signal shifts as expected to low and the game isn't loading. Which would point to U1 being faulty indeed.
It could also be sth wrong further down the line on the Data bus, but these CIA chips are known to fail easily . I would consider changing that first.
I might still be worth checking there's activity on the other lines (ie, the data line might be having issues and not be receiving the data from the tape ) on the cassette port but you'll really need a scope or at least a logic analyser for this. Might be worth double checking with a known working tape deck first just to completely rule that part out