How come Yitzchok wasn't Menachem Avel Yaakov upon Yaakov's hearing that Yosef was deceased? We know Yitzchok knew that Yosef was alive. Nevertheless, when all of Yaakov's sons and daughters came to be Menachem Avel, why didn't Yizchok participate? Didn't that make Yaakov wonder "why isn't my father here with me during this awful time?"
Refer to Bereishis Rabbah 84:21 which says expressly that in front of Yaakov, Yitzchak cried etc. but in private carried on as usual knowing that Yosef was still alive:
וַיָּקֻמוּ כָל בָּנָיו וְכָל בְּנֹתָיו (בראשית לז, לה), כַּמָּה בָּנוֹת הָיוּ לוֹ חֲדָא הֲוַת וְהַלְוַאי קְבָרָהּ, אֶלָּא אֵין אָדָם נִמְנַע מִלִקְרֹא לַחֲתָנוֹ בְּנוֹ וּלְכַלָּתוֹ בִּתּוֹ. רַבִּי יְהוּדָה אוֹמֵר לְאַחְיוֹתֵיהֶם נָשְׂאוּ הַשְּׁבָטִים, הֲדָא הוּא דִכְתִיב: וַיָּקֻמוּ כָל בָּנָיו וְכָל בְּנֹתָיו לְנַחֲמוֹ. (בראשית לז, לה): וַיְמָאֵן לְהִתְנַחֵם, מַטְרוֹנָה שָׁאֲלָה אֶת רַבִּי יוֹסֵי אָמְרָה לוֹ כְּתִיב (דברי הימים א ה, ב): כִּי יְהוּדָה גָּבַר בְּאֶחָיו, וּכְתִיב (בראשית לח, יב): וַיִּנָּחֶם יְהוּדָה וַיַּעַל עַל גֹּזְזֵי צֹאנוֹ, וְזֶה אֲבִיהֶם שֶׁל כֻּלָּם וַיְמָאֵן לְהִתְנַחֵם, אָמַר לָהּ מִתְנַחֲמִים עַל הַמֵּתִים וְאֵין מִתְנַחֲמִים עַל הַחַיִּים. (בראשית לז, לה): וַיֵּבְךְּ אֹתוֹ אָבִיו, זֶה יִצְחָק. רַבִּי לֵוִי וְרַבִּי סִימוֹן אָמְרוּ אֶצְלוֹ הָיָה בּוֹכֶה וְכֵיוָן שֶׁיָּצָא מֵאֶצְלוֹ הָיָה הוֹלֵךְ וְרוֹחֵץ וְסָךְ וְאוֹכֵל וְשׁוֹתֶה. וְלָמָּה לֹא גִּלָּה לוֹ, אָמַר, הַקָּדוֹשׁ בָּרוּךְ הוּא לֹא גִּלָּה לוֹ וַאֲנִי מְגַלֶּה לוֹ. אָמַר רַבִּי סִימוֹן עַל שֵׁם כָּל שֶׁמִּתְאַבְּלִין עָלָיו מִתְאַבְּלִין עִמּוֹ.
“All his sons and all his daughters arose to console him, but he refused to be consoled; he said: For I will descend mourning to the grave, to my son. His father wept for him” (Genesis 37:35). “All his sons and all his daughters arose” – how many daughters did he have? He had one, and if only he had buried her. It is, rather, that a person does not refrain from calling his son-in-law his son and his daughter-in-law his daughter. Rabbi Yehuda says: The tribes married their sisters. That is what is written: “All his sons and all his daughters arose to console him.” “But he refused to be consoled” – a certain noblewoman asked Rabbi Yosei, she said to him: It is written: “For Judah prevailed over his brothers” (I Chronicles 5:2), and it is written: “Judah was consoled, and he went up to his sheepshearers” (Genesis 38:12), and this one, the father of them all, “refused to be consoled”? He said to her: One is consoled for the dead, but one is not consoled for the living. “His father wept for him” – this is Isaac. Rabbi Levi and Rabbi Simon said: When [Jacob] was with him he would weep, but when he would leave him, he would go, bathe, and anoint himself with oil. Why did he not reveal it to him? He said: The Holy One blessed be He did not reveal it to him and I will reveal it to him? Rabbi Simon said: This was based on: Anyone for whom one mourns, one mourns with him.
If one holds that Genesis 35:8 also signifies Rivka's death, then Rivka died when Yaakov reentered Israel. When Joseph "died", Isaac would have been very old and blind and unable to make the journey alone.
Perhaps he was persona non grata after the Shechem incident an was afraid that he would be killed if he was caught by a vengeful Canaanite.
Perhaps Eisav was caring for him and didn't let him visit Yaakov in order to spite Yaakov. (Or Perhaps Isaac knew that Eisav hated Yaakov and didn't want to impose on him to make him attend his brother)
Genesis 35:8 "And Deborah, Rebecca's nurse, died, and she was buried beneath Beth el, beneath the plain; so he named it Allon Bachuth."
This feature appears to be in the Hebrew too. The final sentence, it is unclear who "his father" and "him" are. It could be Yaakov and Yosef but it could also be Isaac and Yaakov, a hint that Isaac was involved in the consoling. Perhaps Yaakov's children exhausted everything there was to say so Isaac didn't try to console him, and rather just wept.
And all his sons and all his daughters arose to console him, but he refused to be consoled, for he said, "Because I will descend on account of my son as a mourner to the grave"; and his father wept for him.