It seems to be permission issue.
As we know:
• To add, modify, and delete anti-spam policies, you need to be a member of the Organization Management or Security Administrator role groups.
• For read-only access to anti-spam policies, you need to be a member of the Global Reader or Security Reader role groups.
You could create a new account and assign Security Administrator role group, then check if this issue persist.
Did it work fine before? Before the issue happened, did you do any modifications, especially about role group?
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